Rio Alto Provides La Arena Update-9,385 Ounces of Gold Produced in Q1

Rio Alto Mining Limited ("Rio Alto" or the "Company") (TSX
VENTURE:RIO)(BVLAC:RIO)(OTCQX:RIOAF)(DBFrankfurt:MS2) is pleased to report that
for its first quarter ended August 31, 2011 pre-commercial gold production from
the La Arena Gold Oxide Mine was 9,385 ounces of gold. The Company is also
pleased to provide an update on activities at La Arena.


Pre-commercial Production

For the June 1 to August 31 period mine production amounted to 1,080,679 tonnes
of ore grading 0.55 grams of gold per tonne ("Au g/t") and waste moved was
916,064 tonnes.




                    Ore        Au    Au Ozs    Au Ozs     Waste  Average Ore
                (tonnes)      g/t    to Pad    Poured   (tonnes)  Tonnes/Day
----------------------------------------------------------------------------
----------------------------------------------------------------------------
June            209,756      0.53     3,574         0   281,731        6,992
July            342,529      0.46     5,044     3,277   300,475       11,049
August          528,394      0.61    10,312     6,108   333,858       17,045
                                                                            
----------------------------------------------------------------------------
Total/Average 1,080,679      0.55    18,930     9,385   916,064       11,747
----------------------------------------------------------------------------
----------------------------------------------------------------------------
                                                                            
Production for Q4, ended May 31, 2011                                       
                                                                            
                375,705      0.54     6,555     2,660   533,325       10,100



Mining during the quarter was from the 3586, and 3532 benches (each bench is
approximately 6m) of the Calaorco Pit. The average grade of these benches
(according to the mine plan used in preparation of the Company's NI 43-101 La
Arena Project, Peru Technical Report with an effective date of July 31, 2010
prepared on behalf of the Company by Coffey Mining Pty Ltd (the "Technical
Report") was 0.44 Au g/t. To-date, the ore mined averaged 0.55Au g/t or
approximately 125% of the ore reserve grade.


During the quarter the Company sold 6,909 ounces of gold at an average price per
ounce of US$1,554 and 1,021 ounces of silver at an average price of US$40.95 per
ounce. Deliveries of gold under the Company's gold prepayment facility amounted
to 1,466 ounces in satisfaction of the July through September 2011 delivery
requirements.


Current guidance for total gold production during 2011 is 50,000 - 60,000 ounces
with 100,000 ounces of gold expected to be placed on the pad by December 31.


The Company expects to achieve commercial production at a consistent rate of
24,000 tonnes of ore per day in November.


Mining and Processing

On May 9, 2011, the Company announced its first gold pour of 1,112 ounces of
gold. This milestone was achieved less than ten months after the Company
received its environmental impact study approval to construct and operate a
24,000 tonnes per day gold oxide mine at La Arena.


Mining at La Arena, from March 2011 to June 2011 was carried out using a
temporary, sub-optimal fleet of mining equipment provided by La Arena mining
alliance partner, GyM Stracon, while orders for larger equipment were
outstanding. In July 2011, the first of fourteen CAT777 haul trucks arrived on
site for introduction to the mining fleet. Also in July, the first of two
Bucyrus RH90 excavators arrived on site. By the end of August, eight CAT777 haul
trucks and one Bucyrus RH90 excavator were operational at the gold oxide mine.
Another six CAT777 and the remaining Bucyrus RH90 excavator were being assembled
to be operational at the end of September. This new equipment allowed the
Company to increase the daily average of ore placed on the pad from 6,922 in
June 2011 to 17,045 tonnes per day in August.


During the quarter, work commenced on the expansion of the adsorption/desorption
processing plant and leach pad at La Arena from a capacity of 10,000 tonnes per
day to 24,000 tonnes per day. The leach pad is expected to be able to
accommodate ore at the rate of 24,000 tonnes per day by mid October and the
processing plant is expected to be operating at a treatment capacity of 24,000
tonnes per day by the end of October. Pad expansion will continue into early
2012 to accommodate next year's pad space requirement.


To date, over a 45 to 60 day period, the Company is achieving approximately
80-85% recovery from run of mine (ROM) leaching. Management estimates that life
of mine recoveries will average close to 90%.


Throughout August 1,057 people were employed by the Company and various
contractors at the La Arena mine site. Approximately 80% of these people were
from the immediate local communities and surrounding areas of the region of La
Libertad. Rio Alto's policy is to promote the training and employment of local
people as the major part of the workforce at La Arena.


A total of three lost time incidents have occurred on site since mining began at
La Arena in March. A total of 38 man days were lost as a result of these
incidents. Safety is a primary focus for management at site and a number of
induction and training initiatives have been implemented to reinforce the
importance of working safely at La Arena. The project has recently recorded its
first 100-day continuous period without a lost time incident.


Geology

There are 2 reverse circulation ("RC") drilling rigs and 4 diamond drill ("DD")
rigs operating on site testing the sulfide ore body and oxide targets. 


Sulphides

During the quarter 4,208 meters of DD core in sixholes were drilled within the
sulphide ore body adjacent to the La Arena Gold Oxide Mine and 5,364 meters of
RC drilling in seventeen holes were completed on the western limit of the
sulphide deposit. The DD drill core is undergoing geotechnical analysis as part
of the Company's sulphide feasibility study. The drill core will be assayed once
this work is completed and the assay results of these holes and the sulphide RC
holes will be released. Rio Alto intends to drill about 35,000m of DD core
within the sulphide deposit as part of the sulphide feasibility study.


Oxides

1,166 meters of RC drilling have been completed in six holes within the newly
discovered Astrid oxide zone. Samples are being assayed and the results will be
announced in the near future. The Company plans to drill approximately fifty
holes for a total of 9,300 meters at Astrid as part of a first phase drilling
program.


As previously announced (see press release dated July 20, 2011) Rio Alto's
geologists are working on a new gold oxide resource estimate incorporating the
results of RC drilling within and around the Calaorco Pit at the La Arena Gold
Oxide Mine.


Due to the positive results achieved from oxide drilling to date, the discovery
of the Astrid oxide zone adjacent to the Calaorco pit and the positive grade
reconciliation achieved in the mining operations, the Company is evaluating the
further expansion of throughput at the La Arena gold oxide project to 36,000
tonnes of ore per day by the end of 2012.


Sulphide Feasibility Study

Rio Alto is pleased to announce that Hatch(TM) was selected as the lead engineer
for the La Arena sulphide feasibility study. Hatch(TM) is a global
multidisciplinary management, engineering and development consultancy providing
services to the mining, metallurgical, energy and infrastructure industries. Its
group companies have more than 8,000 staff in 65 offices on six continents. Its
Lima office is staffed by 75 people. Feasibility study activities initiated
during the quarter were to establish the scope of work for the lead engineer and
the various other sub-contracting engineers; commence drilling for ore resource
and reserve expansion; start geotechnical studies; begin design of a
metallurgical test work program and conceptual site layout. Also during the
quarter, the Company received the results of a pre-feasibility level tailings
deposition plan for the La Arena Sulphide Project completed by Golder
Associates.


Management expects that the sulphide feasibility study will be completed in
approximately 18 months.


Environment, Permitting and Community

On August 1, 2011, the Company appointed Siegfried Arce to the position of Vice
President Environment, Permitting and Community. Mr. Arce has more than 30 years
of experience as a geologist, mining engineer and consultant within the mining,
power, oil & gas, transportation and government sectors in Peru. From 1998 to
2008, Mr. Arce was the President and General Manager of Golder Associates Peru
S.A. and was responsible for growing the company from 2 employees in 1998 to 230
employees in 2008. His principal expertise has been in project management of a
wide variety of resource projects in Latin America with a focus on: conceptual
project design, site selection studies, scoping studies, feasibility studies,
environmental studies, permitting and engineering and construction. Within the
mining industry, Mr. Arce has expertise in planning and managing: exploration
programs, underground mine development, ore transportation systems, underground
mining, and waste management. He has also been involved in the planning and
implementation of ore processing control systems including crushing, grinding
and flotation and in-line slurry analysis for a number of mining operations in
Peru. Mr. Arce's expertise extends to water supply and hydroelectric project
planning from feasibility studies to design and construction management. During
his career, Mr. Arce has worked closely with a number of government agencies and
in 1992 was an advisor to the Ministry of Energy & Mines in Peru. Mr. Arce holds
a Bachelor of Science Degree in Geological Engineering from the Universidad
Nacional Mayor de San Marcos, Peru.


During the quarter, the Company completed the construction of a modern school
designed to accommodate approximately 300 children from pre-school to high
school age. The Company is advancing a number of community focused activities
and is working closely with community leaders in defining and executing a number
of initiatives.


The permitting of a mining operation in Peru involves applying for more than 100
different permits during the life of a project. Rio Alto started the permitting
process for the La Arena Gold Oxide Project after it received the Environmental
Impact Study approval for the project in July 2010. While awaiting for a key
permits to be issued, the Company and its various contractors have obtained
provisional permissions for the use of reagents, fuel, explosives and mining
activities to allow operations at La Arena to commence and continue until final
permits are issued. The Company has a team of people led by Mr. Arce in constant
dialogue and working with the Ministry of Energy and Mines in fulfilling the
permitting requirements.


On July 20, 2011, La Arena SA filed with government authorities an independently
prepared mine closure plan in accordance with Peruvian law. If the plan is
approved in calendar 2011 Rio Alto will be required to post a reclamation bond
of approximately $3.2 million in January 2012.


Enrique Garay, M Sc. P. Geo. (AIG Member), Vice President Geology of Rio Alto,
the Company's nominated Qualified Person pursuant to National Instrument 43-101,
has read and approved the scientific and technical information disclosed in this
news release. For additional information regarding La Arena Oxide Gold Mine and
the sulphide project please refer to the Report, a copy of which is available
under Rio Alto's SEDAR profile at www.sedar.com.


This news release contains certain forward-looking information including
statements concerning the expected timing for achieving a production rate of
24,000 tonnes per day, production expansion target, estimated 2011 gold
production, the timing for delivery of production equipment, the expected timing
for the release of drilling assays, the expected completion of the sulphide
feasibility study, anticipated life-of-mine dump leach recovery, the expected
receipt of operating permits and the timing of a new resource estimate for the
Calaorco Pit of La Arena Gold Oxide Mine. All statements included herein, other
than statements of historical fact, are forward-looking information and such
information involves various risks and uncertainties. There can be no assurance
that such information will prove to be accurate, and actual results and future
events could differ materially from those anticipated in such information. A
description of assumptions used to develop such forward-looking information and
a description of risk factors that may cause actual results to differ materially
from forward-looking information can be found in Rio Alto's disclosure documents
on the SEDAR website at www.sedar.com. Rio Alto does not undertake to update any
forward-looking information except in accordance with applicable securities
laws.


To learn more about Rio Alto Mining Limited, please visit: www.rioaltomining.com
or Rio Alto's SEDAR profile at www.sedar.com.


ON BEHALF OF THE BOARD OF RIO ALTO MINING LIMITED

Alex Black, President & COO
Rio2 (TSXV:RIO)
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