Two BP supervisors charged with manslaughter

Two BP supervisors were charged with involuntary manslaughter for the well blowout that killed 11 workers and unleashed a huge oil spill in the Gulf of Mexico, US prosecutors said Thursday.

A third BP employee was also charged with obstruction of justice for lying about how much oil was gushing out of the runaway well after the Deepwater Horizon rig sank in April 2010.

Attorney General Eric Holder cautioned that more people may yet face prosecution after announcing a deal to settle criminal charges against the British energy giant for $4 billion.

"It's an ongoing investigation," Holder told reporters.

"We'll continue to follow all credible leads and pursue any charges that are warranted."

Holder also noted that the justice department had "failed to resolve" its civil case to determine how much BP should pay in fines under the Clean Water Act and other environmental rules.

Those fines could amount to as much as $18 billion if gross negligence is found.

"We're looking forward to the trial -- which is scheduled to begin in February of next year -- in which we intend to prove that BP was grossly negligent in causing the oil spill," Holder said.

He heralded Thursday's "historic" settlement of BP's criminal charges as a "critical step forward."

"I hope this sends a clear message to those who engage in this kind of reckless conduct that there is a severe penalty to pay and that individuals will be held accountable -- this is not just a company making a plea," Holder told reporters.

Robert Kaluza, 62, and Donald Vidrine, 65 -- the highest-ranking BP supervisors onboard the Deepwater Horizon at the time of the deadly blast -- were accused of grossly negligent conduct which caused the 11 deaths.

"In the face of glaring red flags indicating that the well was not secure, both men allegedly failed to take appropriate action to prevent the blowout," said assistant attorney general Lanny Breuer.

Former senior BP executive David Rainey was charged in a separate indictment with obstructing a congressional investigation and making false statements to law enforcement officials.

"The indictment alleges that Rainey, on behalf of BP, intentionally underestimated the amount of oil flowing from the Macondo well," Breuer said.

"Rainey allegedly cherry-picked pages from documents, withheld other documents altogether and lied to Congress and others in order to make the spill appear less catastrophic than it was."

Rainey faces up to five years in jail if convicted of one charge of obstruction of Congress charge and five years for one count of making false statements to law enforcement.