Updated — Nov. 15, 11:15 p.m. ET
A chemical leak at a DuPont facility in La Porte, Texas, killed four workers Saturday and sent another to the hospital.
The leak happened about 4 a.m. Saturday and involved methyl mercaptan, according to KPRC. Four workers at the facility died from exposure to the chemical, while a fifth who was hospitalized is expected to recover.
DuPont spokesman Aaron Woods told KHOU the leak was the result of a valve failure. The workers' names were not released, but Woods said they included both veterans and newer hires.
Methyl mercaptan is a naturally occurring gas used as a component in insecticides, fungicides, plastics, and jet fuel. The leak was contained by 6 a.m. and the chemical had dissipated later in the day. However, a foul odor reportedly lingered in the area for at least part of the morning.
La Porte is about 25 miles from Houston. Pictures from the scene show emergency responders blocking off roads near the facility.
BREAKING: Four killed after chemical spill at DuPont facility in La Porte http://t.co/AN9i8xdV9T #KPRC #HouNews
BREAKING: 4 DuPont workers dead in La Porte chemical leak. http://t.co/ZrIK9UGV9e
DuPont facilities have previously been investigated for four other accidents.
The U.S. Chemical Safety Board (CSB) announced it was sending a seven-person team to investigate Saturday's fatal leak. The CSB also details four previous investigations into leaks at DuPont facilities. One of those accidents happened in 2010 in Buffalo, New York, and resulted in a single fatality.
The other accidents happened in Belle, West Virginia, over the course of 33 hours in January 2010. An investigation later found that there had been "a series of preventable safety shortcomings," according to the CSB.