A seven person go-team from the U.S. Chemical Safety Board (CSB) begins work this morning at the LaPorte DuPont plant near Houston, trying to determine what caused the toxic chemical leak that killed four workers and sent another to the hospital early Sunday morning.

The workers died when methyl mercaptan, a chemical used as feedstock to make insecticides and fungicide, was released into the air – a leak DuPont said was caused by a malfunctioning container of the gas, according to news reports.

The company said the leak was contained within a few hours and poses no threat to the community of La Porte, Texas, which is approximately 20 miles east of Houston.

The CSB team received a briefing from DuPont yesterday. Managing Director Horowitz said the initial plans are to examine the accident site, conduct initial interviews with witnesses, if any, as well key operators and managers, and to request documentation on a range of relevant activities, such as maintenance histories of key equipment, training, and work schedules.

He added, “Eventually we will construct a timeline of events leading to this tragedy, and issue safety recommendations, if needed. Typically our investigations can take a year or more to complete and be approved and released by the board, but we strive to release key facts and findings as soon as we can as the investigation continues, in order to keep the public updated.”

The CSB has previously investigated four accidents at DuPont facilities; a 2010 phosgene release at the DuPont Plant in Belle West Virginia resulting in one fatality and that same year a hot work accident at the DuPont facility outside of Buffalo, NY, fatally injured one worker. The CSB’s investigations of those incidents can be found at www.csb.gov. 

The CSB is an independent federal agency charged with investigating industrial chemical accidents.