Four workers dead after Houston-area chemical leak Four workers died and a fifth was hospitalized following a chemical leak at a DuPont chemical plant in La Porte, Texas on Saturday. Last Updated Nov 15, 2014 7:49 PM EST LA PORTE, Texas -- Four DuPont workers are dead and another is in the hospital following a chemical leak Saturday at a suburban Houston industrial plant. DuPont company spokesman Aaron Woods says a valve somehow failed on a container of methyl mercaptan, a hazardous chemical used to make insecticides and fungicides, around 4 a.m. Workers were able to get the leak under control within about two hours, CBS affiliate KHOU reported. By then, five workers had already been exposed to the gas. Four people died inside the unit, and a fifth was transported and is recovering in an area hospital. "There are no words to fully express the loss we feel or the concern and sympathy we extend to the families of the employees and their co-workers," plant manager Randall Clements said in a statement. We are in close touch with them and providing them every measure of support and assistance at this time. The employees' tenures ranged from eight months to 40 years, Clements told KHOU, adding that all employees undergo "very extensive training--not only book training, but they must also demonstrate knowledge before you can work in a unit." "The operators were doing the jobs they were trained to do," Clements said. Clements said DuPont would be cooperating with local, state and federal officials investigating the leak. "As part of that investigation, we are conducting our own top-to-bottom review of this incident and we will share what we learn with the relevant authorities," he said. Methyl mercaptan is also commonly used to odorize natural gas -- which has no odor -- for safety purposes. Winds carried a strong odor, similar to rotten eggs, for many miles. Woods said that odor is not hazardous, adding air quality tests in the area came back normal and local emergency officials decided not to issue a shelter-in-place order to the general public. While the chemical is very dangerous in a concentrated form, Woods said once it goes into the air, it dissipates to the point where it is no longer hazardous. The La Porte plant has 320 DuPont employees. Four other companies are also tenants at the complex, which was on lockdown most of the day.