British oil and petrochemicals group BP could be fined more than $18 billion by the US government for its April 2010 Deepwater Horizon oil rig explosion in the Gulf of Mexico, latest reports from the US suggest.

The incident killed 11 workers and released millions of barrels of oil into the Gulf.

Up to now, BP has paid more than $28 billion in damage claims and cleanup costs as well as pleading guilty to criminal charges. Throughout the process, it has claimed that it was not chiefly or solely responsible, placing part of the blame on contractor Halliburton and Transocean.

In a Sept. 4 decision, a US federal judge in the state of Louisiana ruled that BP bore primary responsibility, assigning 67% of the blame to the UK oil giant,  30% to Transocean and 3% to Hallliburton.

Judge Carl J. Barbier said BP had acted "recklessly" and with conscious disregard of known risks." He also raised the possibility of new penalties for violating the US Clean Water Act, totalling $18 billlion, many times exceeding the reserves of $3.5 billion the company has set aside.

BP said in a statement it "strongly disagrees" with the decision and plans to appeal. It added that the ruling was "not supported by the evidence at trial."

State governments along the US Gulf Coast, also may seek damages from the UK group, and civil suits are also pending.