Osisko Reports Fire at Canadian Malartic Milling Plant

Thu May 10, 2012 8:59am EDT

* Reuters is not responsible for the content in this press release.

Osisko Mining Corporation (the "Company" or "Osisko")
(TSX:OSK)(FRANKFURT:EWX) reports that a fire started in the cyclone
separator portion of the Canadian Malartic mill around 11:45 PM last
night. Firefighters have contained and extinguished the fire and we are
now monitoring the mill. Osisko representatives have re-entered the mill
to carry out the preliminary damage assessment. Emergency procedures for
an orderly shutdown were executed by the Osisko team and emergency
services. Emergency services from Malartic and the region responded
promptly. We would like to thank the emergency services teams for their

    Approximately 50 employees were in the plant but no one was injured. At
this time, we have no reason to believe that industrial chemicals were
released in the environment. Regular mining operations are being
maintained outside of the mill area and all employees are back at work.

    Later today we will provide an update to the market setting out the
anticipated schedule to resume full operations at the mill.

    About Osisko Mining Corporation

    Osisko Mining Corporation operates the Canadian Malartic gold mine in
Malartic, Quebec and is pursuing exploration on a number of properties,
including the Hammond Reef Gold Project in Northern Ontario.

    Forward-Looking Statements

    Certain statements contained in this press release may be deemed
"forward-looking statements". All statements in this release, other than
statements of historical fact, that address events or developments that
Osisko expects to occur, are forward looking statements. Forward looking
statements are statements that are not historical facts and are
generally, but not always, identified by the words "expects", "plans",
"anticipates", "believes", "intends", "estimates", "projects",
"potential", "scheduled" and similar expressions, or that events or
conditions "will", "would", "may", "could" or "should" occur including,
without limitation, consequence of this incident on operations at
Canadian Malartic operations. Although Osisko believes the expectations
expressed in such forward-looking statements are based on reasonable
assumptions, including, without limitation, that all technical,
economical and financial conditions will be met in order to warrant
further development of its Hammond Reef project and that the diligent
ongoing optimizing of its operations at the Canadian Malartic mine
including the installation of the secondary crushing circuit will be
achieved and will, accordingly, improve its operating performance, such
statements are not guarantees of future performance and actual results
may differ materially from those in forward looking statements. Factors
that could cause the actual results to differ materially from those in
forward-looking statements include gold prices, access to skilled
consultants, mining development personnel, results of exploration and
development activities, Osisko's limited experience with production and
development stage mining operations, uninsured risks, regulatory changes,
defects in title, availability of personnel, materials and equipment,
timeliness of government approvals, actual performance of facilities,
equipment and processes relative to specifications and expectations,
unanticipated environmental impacts on operations market prices,
continued availability of capital and financing and general economic,
market or business conditions. These factors are discussed in greater
detail in Osisko's most recent Annual Information Form and in the most
recent Management Discussion and Analysis filed on SEDAR, which also
provide additional general assumptions in connection with these
statements. Osisko cautions that the foregoing list of important factors
is not exhaustive. Investors and others who base themselves on
forward-looking statements should carefully consider the above factors as
well as the uncertainties they represent and the risk they entail. Osisko
believes that the expectations reflected in those forward-looking
statements are reasonable, but no assurance can be given that these
expectations will prove to be correct and such forward-looking statements
included in this press release should not be unduly relied upon. These
statements speak only as of the date of this press release.

John Burzynski
Vice-President Corporate Development
(416) 363-8653

Sylvie Prud'homme
Director of Investor Relations
(514) 735-7131
Toll Free: 1-888-674-7563

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