A federal judge has ruled the oil giant BP was “grossly negligent” in the lead-up to the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, the worst in U.S. history. The ruling could force BP to pay up to $18 billion in additional fines. Attorney General Eric Holder praised the ruling in Washington.

Attorney General Eric Holder: “We are pleased that the district court in New Orleans has found that the largest oil spill in United States history was caused by BP’s gross negligence and willful misconduct. The court’s findings will ensure that the company is held fully accountable for its recklessness.”

The ruling also found BP subcontractors Transocean and Halliburton “negligent” in the accident. BP says it will immediately appeal.