By Collin Eaton
HOUSTON (Reuters) - A massive explosion at a machine shop ripped through a Houston neighbourhood early on Friday morning, killing at least two people and damaging homes while sending out blast waves for miles.
The pre-dawn explosion devastated two working-class neighbourhoods surrounding the Watson Grinding and Manufacturing facility in northwest Houston, leaving behind collapsed and smouldering wreckage on the grounds and knocking several nearby homes off their foundations.
Houston Fire Chief Samuel Pena said early indications pointed to a leak of propylene gas, a colourless, flammable, liquefied gas with several industrial uses. But Police Chief Art Acevedo said that was "just a huge assumption" and cautioned that the investigation could take several days, weeks or months.
Officials stressed that they had no reason to believe the explosion was intentionally triggered.
The multi-agency probe will focus primarily on whether any regulatory violations were committed by either Watson Grinding or its vendors, Acevedo said, adding the company was cooperating fully.
While investigators sought to positively identify the two victims, there is a "high probability" they were two men who worked for the company, Acevedo said.
Numerous homes had windows blown in. Others were surrounded by shattered piles of debris.
"I thought it was thunder," said Bruce Meikle, 78, an owner of nearby manufacturer ChemSystems, who heard the explosion from his home about a mile (1.6 km) from the scene.
The force of the blast bent the metal loading doors at his business and caused minor damage inside, he told Reuters.
Paul Crea, 59, a chemist who works for Meikle, said the blast woke him 10 miles (16 km) away in Katy, a Houston suburb, and his dogs bellowed at the sound.
Acevedo asked people as far as a mile (1.6 km) away to search their yards and neighbourhoods for evidence.
"Look for any debris, any body parts, anything that may be related," Acevedo said.
Harris County Sheriff Ed Gonzalez said the blast was felt as far away as 14 miles (22 km), based on social media reports.
The moment of the explosion, around 4:25 a.m. CST (1025 GMT), was captured on video by a home security camera. It showed a blinding flash in the distance followed by a fireball.
Firefighters secured a 2,000-gallon propylene tank outside the building and would allow any remaining fires to burn out, Pena said.
Rescue crews fanned out to examine nearly 200 homes.
"Some of them are off the foundation, the ones especially that are closer to the explosion site," Pena said.
A temporary shelter was established for people left homeless.
Houston, an oil and gas industry hub, is the fourth largest city in the United States with a population of some 2.3 million.
(Reporting by Collin Eaton, Peter Szekely and Bhargav Acharya; Writing by Daniel Trotta; Editing by Alex Richardson, Frances Kerry, Jonathan Oatis and David Gregorio)