A gas explosion on the Deepwater Horizon oil rig in the Gulf of Mexico last year killed 11 workers and resulted in one of the worst oil spills in history. A U.S. government investigation into the accident concluded BP, Transocean and Halliburton committed a series of regulatory violations at the site.
An October report listed seven violations for BP and four each for Transocean and Halliburton.
Michael Bromwich, outgoing director of the Bureau of Safety and Environmental Enforcement, said during his last briefing before stepping down Thursday that more charges are on the way.
"My understanding is that the new regulatory violations will be the result of that deeper dive into some of the underlying materials," he was quoted by the Platts news service as saying.
A report from U.S. regulators determined that the blowout that led to the gas explosion that sunk the Deepwater Horizon platform came from the failure of a cement barrier.
On Thursday, U.S. Coast Guard Rear Adm. James Weston replaces Bromwich as part of a federal reorganization. Bromwich stays on through the end of the year as a special adviser to the U.S. interior secretary.