WASHINGTON (AP) -

 A government warning about the dangers of increased use of trains to transport crude oil is giving a boost to supporters of the long-delayed Keystone XL pipeline.
    
U.S. and Canadian accident investigators urged their governments Thursday to impose new safety rules on so-called oil trains, warning that a "major loss of life" could result from an accident involving the increasing use of trains to transport large amounts of crude oil.
    
Pipeline supporters say the warning highlights the need for Keystone XL, which would carry oil derived from tar sands in western Canada to U.S. Gulf Coast refineries.
    
North Dakota Sen. John Hoeven said the yearslong review of Keystone has forced oil companies to look for pipeline alternatives in the booming Bakken (Bahk-kenn) region of North Dakota and Montana.