DuPont has agreed a $3.1 million (£2.4 million) settlement with the US Environmental Protection Agency (EPA) and Department of Justice (DOJ) to resolve chemical accident prevention violations related to a methyl mercaptan leak that killed four workers at the company’s now-shuttered insecticide plant in La Porte, Texas, in 2014.

The incident occurred when workers were attempting to clear a solid mercaptan hydrate blockage in pipework, and the gas was diverted into vent pipework that lacked appropriate sensors.

The complaint identifies 22 separate violations of the US Clean Air Act’s risk management programme, including failure to develop and implement written operating procedures, and breaches of ‘mechanical integrity’.

Beyond this EPA and DOJ review, the US Occupational Safety and Health Administration (OSHA), and Chemical Safety Board (CSB) launched separate probes of the incident.

DuPont spokesman Gregg Schmidt says the company has cooperated fully with these investigations and believes that the settlement is a ‘reasonable resolution’. He states that DuPont ‘does not accept or agree with many of the government’s allegations’, but that it will nevertheless work collaboratively to improve its process safety practices.

In 2015, OSHA fined DuPont $372,000 for safety violations and training deficiencies at the La Porte plant, while the CSB uncovered flaws in DuPont’s ventilation and toxic gas detection systems. DuPont has also reportedly settled with the family of at least one of the four victims for an undisclosed sum.