The Associated Press quoted a person familiar with the deal as saying two BP employee face manslaughter charges in the case. BP, in addition to paying billions in fines, will plead guilty to obstruction for lying to Congress about how much oil was pouring out of the ruptured well, the AP reported.
BBC business editor Robert Preston reported that BP is "thought to be relieved" that it has reached a settlement because the potential liability was unlimited. The BBC said details are expected to be confirmed later by the Department of Justice.
The reported settlement would dwarf the largest previous corporate criminal penalty assessed by the Department of Justice - the $1.2 billion fine imposed on drug maker Pfizer in 2009.
The explosion and fire aboard the Deepwater Horizon rig on April 20, 2010, killed 11 workers and set off a spill which continued for 87 days, fouling large areas of the southern coast of the United States.
The rig sank and an estimated 200 million gallons of crude oil gushed out of the well, fouling extensive areas of the southern U.S. coast and disrupting tourism and commercial fishing
In advance of an expected settlement, BP said in a statement that "no final agreement has yet been reached" and that any such deal would still be subject to court approvals, the Associated Press reported.
Shares in BP PLC were down 0.8% at 422 pence in early trading in London.
In its earlier statement, BP said any proposed settlement would not include civil claims under the Clean Water Act and other legislation, pending private civil claims and state claims for economic loss.
BP has booked provisions of $38.1 billion to cover its liabilities from the incident, but the company has said the final cost remained highly uncertain. BP also recently announced that it expects to make the final payment this year to a $20 billion trust fund to cover damage from the blowout.
In March, BP announced a settlement estimated at $7.8 billion with more than 100,000 individuals and businesses for medical and economic losses.
In January 2011, a U.S. presidential commission found that the spill was caused by time-saving, cost-cutting decisions by BP, rig owner Transocean and cement contractor Halliburton.
In September last year, a team of Coast Guard officials and federal regulators concluded BP bears ultimate responsibility. Their report found BP violated U.S. regulations, ignored crucial warnings and made bad decisions during the cementing of the well a mile beneath the Gulf of Mexico.
(Copyright © 2012 USA TODAY)