“The mistakes made during the start up of this unit were surprising and deeply disturbing,” BP Products North America president Ross Pillari was quoted as saying.

Pillari said a tower in the facility was greatly overfilled and then overheated.

“The fluid level in the tower at the time as nearly 20 times higher than it should have been,” he said.

In addition, the base temperature was 302 degrees Fahrenheit, 25 degrees higher than it should have been.

Failure to follow emergency procedures also contributed to the scale of the disaster and increased the number of deaths and injuries. Workers were not evacuated as soon as it became clear there was dangerous pressure building up in the vessel and explosive vapours were being released.

Many workers located in trailers nearby, which may have provided the source of ignition for the explosion, were injured.

BP also found using a flare system would have reduced the severity of the explosion. The facility used a blowdown stack which is being phased out of use by the industry.

BP said it was taking action against supervisory and hourly employees, with punishment ranging from sackings to warnings.