DuPont has been fined $99,000 and strongly criticized by the Occupational Safety and Health Administration (OSHA) for failing to prevent the death of four employees at a chemical plant in November 2014.

The agency cited DuPont for 11 safety violations at its Lannate/API manufacturing facility in La Porte, Texas, which produces crop protection materials and chemicals. It said that the company must undertake scores of safety upgrades to prevent future accidents.

"Four people lost their lives and their families lost loved ones because DuPont did not have proper safety procedures in place," said Assistant Secretary of Labor for Occupational Safety and Health Dr. David Michaels. "Had the company assessed the dangers involved, or trained their employees on what to do if the ventilation system stopped working, they might have had a chance."

The fatal incident occurred when a worker opened a drain on a vent line and methyl mercaptan gas was unexpectedly released. Two co-workers who came to her aid were also overcome, and a fourth co-worker — the brother of one of the men — tried to rescue them but was unsuccessful. All four people died in the building.

DuPont spokesman Aaron Woods told the Houston Chronicle that steps have already been taken to "prevent this from ever happening again" and the unit remains shut down while the company reviews its process safety management systems.

"Our response to this tragedy reinforces our absolute focus on safety and enables us to learn from it so that we can find ways to be an even better company," he added.