"In the interest of justice" a U.S. court dismissed manslaughter charges against BP engineers on the Deepwater Horizon rig at the time of the 2010 accident.

The U.S. District Court for the Eastern District of Louisiana dismissed charges filed against BP engineers Robert Kaluza and Donald Vildrine, who were tasked with testing processes at the Macondo well that eventually failed beneath the Deepwater Horizon rig.

A cascading string of events led to what the industry calls a blowout, which triggered explosions on rig that eventually left 11 workers dead and sparked the worst accidental offshore oil spill in the history of the industry.

Defendants Kaluza and Vildrine were charged with 11 counts of involuntary manslaughter and one charge of violating the federal Clean Water Act. Manslaughter counts were dismissed by a lower court in 2013.

"The United States now moves to dismiss counts 1 through 11 without prejudice on the grounds that dismissal is in the interests of justice," the U.S. district court said in its ruling.

A federal indictment charged the duo with ignoring signals on the Deepwater Horizon that the Macondo well was on the brink of failure.

"Defendants Kaluza and Vildrine, in violation of their duty of care, negligently and grossly negligently failed to maintain control of the Macondo well," the federal indictment read.

In November, BP engineer Kurt Mix issued a guilty plea to lesser charges of obstruction and was sentenced to six months of probation. Mix was tasked with determining the amount of oil leaking from the Macondo well and was prosecuted for deleting text messages and other correspondence related to those calculations.

The defense team for Mix argued most of the deleted messages were not germane to the spill, which showed there was no cover-up attempt.