A U.S. oil company, Anadarko Petroleum, has agreed to pay $4 billion to BP to cover the costs related to last year’s devastating oil spill in the Gulf of Mexico.

The explosion of the Deepwater Horizon oil rig on April 2010 killed 11 workers and sent 5 million barrels of oil pouring into the waters off the southern coast of the United States. It was the worst oil spill in U.S. history.

BP on Monday announced a settlement of a dispute with Anandarko, which owned 25 percent of the rig. But the London-based company remains caught up in legal issues involving two other contractors connected to the offshore well. Switzerland’s Transocean operated the well and the U.S.-based Halliburton was responsible for cementing the well.

BP says damage claims from individuals and businesses, along with government fines, could total $42 billion.