Managers who were onboard the doomed Deepwater Horizon oil rig may face manslaughter charges over the deaths of 11 workers in last year's mega-disaster that swamped the Gulf of Mexico with tar and crude.

"People familiar with the matter" reportedly informed Bloomberg News of the possible charges. They also said that federal investigators were looking into whether or not executives with BP, like former CEO Tony Hayward, made false statements in their testimonies before Congress.

Following the spill, the largest ever manmade environmental disaster in the United States, Washington imposed a moratorium on deepwater drilling in the Gulf of Mexico, which it lifted in October.

While the U.S. government did take a lead role in the investigation, the rig's owner, Transocean, handled the salvage operations, where at least part of the investigators' data comes from.

In addition to BP and Transocean, investment firms Anadarko and Mitsui had a stake in the salvage, after putting up 25 percent and 10 percent of the capital for the deepwater drilling exploration.

They could be liable for those percentages of any damages awarded in litigation, unless they can prove "gross negligence or wilful misconduct" on the part of BP or Transocean. If an investigation does level charges of manslaughter at BP managers on the rig that day, it could help other parties to the litigation prove claims of negligence.

Cameron International, which made the blowout prevention system that was supposed to stop the leak, and Halliburton, which supplied a crew to concrete the well, are also likely to be involved as they have a legal and financial incentive to prove that responsibility for the disaster lay elsewhere.

Federal investigators were also trying to determine how much BP would pay in fines for the 4.9 million barrels of crude that gushed out of the runaway well before finally being capped on July 15.

Fines under the Clean Water Act range from $1,100 per barrel spilled to as high as $4,300 per barrel spilled, if negligence is proven, meaning BP could theoretically face fines of up to $17.6 billion.

With AFP.