BP is to pay a record fine of $US50.6 million for failing to correct safety hazards at its Texas City refinery where an explosion killed 15 people in 2005.
The US Occupational Safety & Health Administration said the penalty "rightly reflects BP's disregard for workplace safety".
BP has also agreed to spend $US500 million on fixing safety problems at the refinery.
The fine is the largest imposed by OSHA, which is part of the Labour Department.
The BBC reports OSHA is still trying to collect another $US30 million from the company for other penalties that BP is contesting.
The company paid a $US21.3m fine to OSHA in 2005 and entered into a four-year agreement to repair hazards at the refinery.
In 2007, BP agreed to pay $US373 million to settle a number of criminal and civil charges.