(MCT) — LOS ANGELES — Laying the blame for the deaths of 11 rig workers in the Deepwater Horizon explosion and Gulf of Mexico oil spill on BP, federal prosecutors announced Thursday that two BP supervisors have been charged with manslaughter and the company will pay a $4 billion criminal fine, the largest in U.S. history.

“Those deaths were in fact unnecessary,” U.S. Attorney General Eric Holder said in New Orleans, adding that the federal investigation continued into the 2010 Deepwater disaster and the nation’s biggest offshore oil spill. “Our work is far from over.”