A chemical used to manufacture insecticides and fungicides at DuPont's plant in La Porte, Texas, leaked on Saturday, killing four workers and injuring one.

The five victims were conducting routine maintenance when methyl mercaptan leaked at around 4 a.m., according to DuPont spokesman Aaron Woods. The chemical is stored as a liquid, but when released in the atmosphere and mixes with oxygen, turns into gas.

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Woods said that DuPont, which withheld the personal information of the victims on request of their families, doesn't still know how the leak began. But it took the company two hours to contain the chemical, reports Chron.com, which named at least two of the victims based on information from their relatives.

They are Robert Tisnado, 39, and his bother Gibby Tisnado, 48. The two others were a long-time employee who had worked with the firm for 40 years and a new hire barely eight months on the job, said Randall Clements, plant manager.

Woods said it is the first incident of chemical leak for DuPont that uses the methyl mercaptan for its crop protection unit, one of the two DuPont divisions located on its 800-acre property which is also partly leased to other companies.

DuPont ordered the workers in its facility to remain where they were at the complex until 4 p.m. The order gave DuPont enough time to replace the defective valve and hold air quality tests.

DuPont has been operating the plant since 1946 where it produces chemicals for a variety of industrial and household uses. The firm notified the Occupational Safety and Health Administration, the Environmental Protection Agency and the Texas Commission on Environmental Quality of the Saturday chemical leak.

Woods said, "We know something wrong happened today and we are going to do the proper investigation to make sure it doesn't happen again."

He added that the company is focused on the four employees who died because of the leak, their families, and the one worker who is still in the hospital. A full probe would follow to ensure the incident won't be repeated in the future.

TagsduPont, chemical leak