The U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA) has placed DuPont in its Severe Violator Enforcement Program and proposed further fines following an accident at a chemical plant in November 2014 in which four employees died.

The workplace health agency had already proposed in May to fine the company $99,000 for safety violations related to the leak of methyl mercaptan that killed four workers. Those violations prompted OSHA to expand its inspection to other parts of the manufacturing facility in La Porte, Texas, where the agency says it found additional hazards.

As a result, OSHA has issued citations to DuPont for three willful, one repeat and four serious violations.

The agency has proposed penalties of $273,000 for these new violations. It also placed the company in its Severe Violator Enforcement Program, which concentrates inspections on employers who have “demonstrated indifference towards creating a safe and healthy workplace by committing willful or repeated violations, and/or failing to abate known hazards”.

“DuPont promotes itself as having a ‘world-class safety’ culture and even markets its safety expertise to other employers, but these four preventable workplace deaths and the very serious hazards we uncovered at this facility are evidence of a failed safety program,” commented Dr. David Michaels, Assistant Secretary of Labor for Occupational Safety and Health.

The fatal incident in November 2014 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.