DEER PARK, Texas – At least two people are dead and 35 others were treated after a chemical release at an industrial plant in Deer Park.

Hydrogen sulfide is the gas and the release shut down both sides of Highway 225 and put the entire City of Deer Park into a shelter-in-place mode with residents told to close their windows and doors and to turn off their air conditioning. The City of Deer Park has lifted the shelter-in-place as of 9:30 p.m.

Authorities say the release happened at the PEMEX facility at 5900 SH-225.

Dozens of emergency vehicles could be seen from the Sky2 helicopter responding to the facility Thursday evening.

The City of Pasadena says the chemical released was hydrogen sulfide and the Pasadena Fire Department issued a shelter-in-place for all areas north of Spencer Highway.

The shelter-in-place has since been lifted for Pasadena after Harris County Pollution Control completed air monitoring and gave the city the all-clear.

Hydrogen sulfide is one of the leading causes of workplace gas inhalation deaths in the U.S., according to the Occupational Safety and Health Administration (OSHA).

It’s highly flammable and toxic, according to OSHA, even at low concentrations. It’s colorless smells like rotten eggs at low concentrations.

OSHA’s overview of hydrogen sulfide says:

It is heavier than air and may travel along the ground

It can build up in low-lying areas, and in confined spaces including enclosed, poorly-ventilated areas

After a while at low or more quickly at high concentrations, you can no longer smell it to warn you it’s there

It can quickly, almost immediately, overcome unprepared workers, including rescue workers

Effects, even at low levels, range from mild headaches or eye irritation to very serious unconsciousness and death

SH-225 was shut down as authorities have responded to the facility. Deer Park’s mayor said the highway will reopen shortly.

All EMS units have left the facility because they don’t believe anyone else is injured. However, for safety reasons, officials haven’t been able to make it far inside the plant so it is possible there are other victims inside the facility. Sheriff Ed Gonzalez said it may be another seven to eight hours before officials can get inside.

“We don’t know if there could be more, we just haven’t been able to actually make entry into the unit itself because, again, its dynamic and we want to make sure we render the area safe,” Gonzalez said.

Air monitoring equipment remains in the area and decontamination protocols are being implemented.

Deer Park’s mayor, Jerry Mouton Jr., says even though residents have been smelling a rotten egg smell, all data coming from air quality monitoring has produced no evidence of any danger in the community.

“We made these decisions based on the air monitoring data that was being done inside the facility and outside the facility by at least two to three different monitoring’s,” he said.

PEMEX released a statement on the incident:

“PEMEX Deer Park confirms that a gas release was reported at one of our operating units at 4:40 p.m. The incident is contained to our site and has been isolated.

Members of our Emergency Response Team, Channel Industrial Mutual Aid (CIMA) and Harris County Emergency Management personnel and other government agencies are on site and responding to the situation.

Our primary concerns are to ensure the safety of everyone involved and to secure the facility. Out of an abundance of caution, State Highway 225 has been temporarily closed.

Some members of the community may see flaring as we safely contain the situation. We are closely monitoring air quality and are not detecting any offsite impacts.”

History of PEMEX

PEMEX is the Mexican state oil company Petroleos Mexicanos.

It took control of the Deer Park facility in January of 2022 after buying the majority stake of the refinery from Shell.

At that time, the facility processed up to 340,000 barrels of crude a day. PEMEX produces the following products, according its website:

Altamira crude oil

Istmo crude oil

Maya crude oil

Olmeca crude oil

Talam crude oil

On the company’s two-year anniversary last January, Pemex CEO Octavio Romero Oropeza told employees in a Facebook post that the Deer Park facility paid for itself in the first year of production. Oropeza said year two brought increased efficiency and profits at the plant.

Harris County Judge Lina Hidalgo released a statement on the incident: