DuPont 4 killed - Several employees of the chemical processing company were affected after a valve malfunction led to the leakage of dangerous gas in its La Porte plant on Saturday morning.

Plant manager Randall Clements has revealed that the leakage of methyl mercaptan started at about 4: a.m. The leak was reportedly put under control two hours later - at 6:00 a.m. But by then five employees had already suffered from overexposure to the chemical, which is used to make pesticides.

The identities of the DuPont 4 killed have not been officially disclosed by the company. However, Clements said among the DuPoint 4 killed, one employee had been with the company for up to 40 years and another had been employed only a few months earlier.

12News has reported that one of the DuPont 4 killed, whom Clements says had worked with the company for only a few months, is a female. Crystle Wise is reported to have worked with DuPont for only 8 months and was planning to move to Houston before her death.

Meanwhile, family members have revealed that 2 of the DuPont 4 killed in the methyl mercaptan leakage were brothers, who had both been with the company for about 6 years. The brothers have been identified as Robert and Gilbert Tisnado.

Relatives of the Tisnado brothers say Gilbert had been trying to save Robert - who worked in the area where the leakage occurred - before they were both killed.

The DuPont 4 killed had been responding to a leakage of a very dangerous chemical. Methyl mercaptan (also known as methanethiol) is a colorless gas, which develops a distinctive rotten-egg smell when it is released in the air. It is believed that the workers perceived the smell and were attempting to stop the leakage when they died. Methyl mercaptan can be lethal to humans when it is released and inhaled in a confined space.

Meanwhile, a fifth worker, who was also exposed with the DuPont 4 killed, has been admitted at the Bayshore Hospital. Close sources say he is responding to treatment. At least two other workers in the unit are reported to have escaped the exposure.

Clements says all DuPont employees receive both theoretical and practical training. He revealed that the company is cooperating with the State investigators in the incident, which it is also investigating privately.

"We will share what we learn with the relevant authorities," he said.

The spokesman for DuPont Aaron Woods says it is unclear why the valve malfunction occurred. According to Woods, this is the first leakage in the facility, which employs over 300 hands.

Reports indicate that the smell of methyl mercaptan was evident in the air in many areas around the plantation several hours after the accident that led to the DuPont 4 killed. But Woods says air quality tests have confirmed that the gas doesn't have the concentration to be lethal in the open air.

Nonetheless, experts from the U.S. Chemical Safety Board are reportedly investigating the death of the DuPont 4 killed and the safety of the air in the La Porte area in light of the leakage.