HOUSTON (AP) — A massive explosion Friday leveled a warehouse in Houston, leaving at least two people dead, damaging nearby buildings and homes and rousing frightened residents from their sleep miles away, authorities said.

The explosion happened about 4:30 a.m. inside a building at Watson Grinding and Manufacturing, which makes valves and provides thermal-spray coatings for equipment in various industries, authorities said. The building was reduced to burning rubble and debris, and some of the surrounding buildings suffered heavy damage to parts of their walls and roofs.

Police Chief Art Acevedo confirmed the deaths Friday and said it was likely both people worked for the company. He said a family member of one of the people suspected to have died was a U.S. Marine currently training at Camp Lejeune, North Carolina, and called on the Marines to let the man return to Houston.

Authorities don’t believe the explosion was intentional though a criminal investigation is underway, Acevedo said.

“Do a search around your own home and your own neighborhood, even if you’re a mile away from this location,” Acevedo said. “Look for any debris, any body parts, anything that may be related. If you find anything in your immediate home, in your yard, don’t touch it. Just call the Houston Police Department so we can respond.”

Houston Fire Chief Samuel Pena said hazardous materials crews have secured the valve on a 2,000-gallon tank of propylene that had been leaking. Propylene is a colorless gas used to produce chemicals in plastics, synthetic rubber and gasoline. It is highly flammable and can explode in a fire. People exposed to propylene can become dizzy and light-headed, and the gas can also cause liver damage.