A congressional committee is investigating a much criticized plea deal that proposes to fine oil giant BP PLC $50 million for its criminal responsibility in a deadly 2005 explosion at its Texas City refinery.

The House Committee on Energy and Commerce has sent a letter to U.S. Attorney General Michael Mukasey saying it is questioning the Justice Department's agreement to have a BP subsidiary plead guilty to a violation of the Clean Air Act. Besides the fine, the company would get three years of probation.

The blast killed 15 people and injured more than 170 others at the refinery about 40 miles southeast of Houston.