(Reuters) The U.S. Chemical Safety Board (CSB) said that 27,000 pounds (13.5 tons) of deadly hydrogen sulfide gas was released at Pemex's Deer Park, Texas, refinery on Oct. 10, causing the deaths of two contract workers.
The board's probe is focusing on the management of maintenance work and emergency response by Mexico's state-owned oil and gas firm, the agency said in a statement posted online late on Wednesday.
Two contract workers employed by Repcon were performing maintenance when they partially opened a flange releasing the hydrogen sulfide gas, the board said.
Thirteen other people were injured in the release that the board said lasted for about an hour. The Houston suburbs of Deer Park and Pasadena, Texas, ordered residents to remain indoors during the release.
"Hydrogen sulfide is a highly toxic substance that can result in serious injury and death even at low concentrations," said CSB chairperson Steve Owen in a statement. "This dangerous incident resulted in the death of two workers and put others workers and the surrounding communities at very serious risk."
Multiple lawsuits seeking millions of dollars in damages from Pemex and former refinery owner Shell Plc have been filed by lawyers on behalf of surviving family members, injured workers and area residents.
The CSB is authorized under the U.S. Clean Air Act to find the root causes of chemical plant accidents.
In addition to the CSB, the Occupational Safety and Health Administration and the Texas Commission on Environmental Quality are among other agencies probing the incident.
