MONTREAL, CANADA--(Marketwire - April 20, 2011) -OSISKO MINING CORPORATION (TSX:OSK)(FRANKFURT:EWX) and OREX EXPLORATION INC. (TSX VENTURE:OX)(FRANKFURT:O5D) would like to inform shareholders that Osisko Mining Corporation has recently begun a new exploration drilling campaign at Orex's wholly-owned Goldboro Gold Property. This drilling campaign includes nine holes for approximately 2,400 metres on two areas of the Goldboro Gold Property. The areas to be drilled include: 1) a 600-metre long gap between West Goldbrook and Dolliver Mountain, where there is no record of previous drilling due to a large bog that limited access; and 2) a 750-metre long gap from East Goldbrook to the east property boundary.

Three diamond drill holes (750 metres) are planned spaced 200 m apart in the West GoldBrook – Dolliver Mountain gap where there is no record of previous drilling. At the east end of the gap, 2010 drill hole number OSK10-09 yielded 36.5 metres (m) grading 1.07 grams per tonne (g/t) gold (Au) and containing a 10.5 m interval grading 2.15 g/t Au at a vertical depth between 150 m to 200 m below surface. The mineralized zone is projected to extend up-plunge westerly towards surface in the area to be drilled (refer to news release of June 10, 2010).

Six drill holes (1,650 metres) are planned on 3 sections spaced 250 m apart from East Goldbrook to the east property boundary. In 2010, reverse circulation (RC) drilling was completed along a fence of closely spaced holes (25 to 50 metres apart) across the indicated trend of mineralization in this area. Bedrock chip samples from 6 RC holes yielded grades above 0.1 g/t Au, within a 250 m-wide mineralized corridor extending eastward from East Goldbrook. Three of these RC holes contained bedrock chip samples with grades above 1.0 g/t Au specifically; 1.38, 10.85 and 25.65 g/t Au respectively (refer to news release of November 18, 2010).

Option on Goldboro Gold Property Granted to Osisko Mining Corporation

In order to acquire a 50% undivided interest in the Goldboro Gold Property on or before September 29, 2013 (the Initial Option), Osisko Mining Corporation shall incur exploration and development expenditures in the amount of at least $1,500,000 on or before September 29, 2010; in the aggregate amount of at least $3,500,000 on or before September 29, 2011; and in the aggregate amount of at least $8,000,000 over the following two years, that is, on or before September 29, 2013. Osisko Mining Corporation may, at its sole discretion, accelerate and apply exploration and development expenditures to future years' expenditures and, accordingly, the Initial Option may be exercised sooner. Osisko Mining Corporation shall solely fund a prefeasibility study to earn an aggregate 60% interest (that is, an additional 10% interest) in the Property on or before September 29, 2015 (the Additional Option).

About Osisko Mining Corporation

Osisko Mining Corporation is currently developing the Canadian Malartic gold deposit in Quebec and evaluating adjacent areas for a large-scale open pit, bulk tonnage mining operation. The Canadian Malartic deposit currently represents one of the biggest permitted gold reserves in Canada, and is still growing through ongoing drilling on new mineralized zones.

About Orex Exploration Inc.

Orex Exploration Inc. is a Canadian-based junior resource and exploration company trading under the symbol OX on the TSX Venture Exchange and O5D on the Frankfurt Stock Exchange. The Company holds a 100% interest in the Goldboro Gold Project in Nova Scotia.

The technical information contained in this news release has been prepared by Mr. Alex Horvath, B.A.Sc., P. Eng., of A. S. Horvath Engineering Inc. (Ottawa, Ontario), Technical Advisor to Orex, who is a Qualified Person under National Instrument 43-101 regulations.

Neither the TSX Venture Exchange nor its regulation services provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this news release. The statements made in this news release that are not historical facts are "forward-looking statements" and readers are cautioned that any such statements are not guarantees of future performance, and that actual developments or results, may vary materially from those in these "forward-looking" statements.

Contact Information:

Orex Exploration Inc.
Mark Billings
President & CEO

Frontline Communications
Leo Karabelas

Osisko Mining Corporation
John Burzynski
Vice-President, Corporate Development

Osisko Mining Corporation
Sylvie Prud'homme
Manager, Investor Relations
Toll-free : 1-888-674-7563