Four Texas workers died and a fifth was hospitalized Saturday morning after a hazardous gas leak at a DuPont chemical plant east of Houston.

The workers were overcome about 4 a.m. Central Standard Time, apparently as they were responding to the leak of the gas, methyl mercaptan, according to the plant’s manager, Randall Clements.

Methyl mercaptan is mixed with odorless natural gas to give it its characteristic rotten-egg smell.

The company said the leak was contained at about 6 a.m. The worker who was not seriously injured was being hospitalized overnight for observation.

The leak spread a stench across broad areas of La Porte, an industrial town on the Gulf of Mexico about 20 miles east of Houston, but the company said it posed no hazard to the community.