PASADENA, Texas (AP) — One person died and several others were injured Thursday when a chemical was released at a Houston industrial plant, a Texas sheriff said.

Authorities warned nearby residents to stay inside and close doors and windows.

One of the people injured was transported to a hospital by a helicopter, Harris County Sheriff Ed Gonzalez wrote on the social platform X. City officials in Pasadena, a Houston suburb, told residents on social media that hydrogen sulfide had been released at a Shell Pemex facility.

Television news crews showed multiple ambulances and emergency vehicles at the scene.

Gonzalez said preliminary information indicated it was a “chemical release” but did not elaborate. The plant is located in the suburb of Deer Park, where city officials issued a shelter-in-place order for nearby residents “out of precaution.”

Houston is the nation’s petrochemical heartland and is home to a cluster of refineries and plants.