Nine people died at the Crandall Canyon mine last year, six of them miners trapped by a collapse and three rescuers killed by another cave-in.

Murray Energy, which operated the mine, ignored signs of problems, the Senate Health, Education, Labor and Pensions Committee said. Sen. Edward Kennedy, D-Mass., said that there should be a criminal investigation of the company and the Mine Safety and Health Administration, The Salt Lake Tribune reported.

The company "failed to tell federal regulators about these dangers, conducted unauthorized mining and -- as a result -- exposed its miners to serious risks," Kennedy said in a statement.

"MSHA also unconscionably failed to protect miners by hastily rubber-stamping the plan," he added. "This is a clear case of callous disregard for the law."