The blast happened around 4:15 a.m. local time (5:15 a.m. ET) at 4525 Gessner Road, about an 18-mile drive northwest of downtown, officials said.
Video posted to Twitter from a camera that was mounted to a home window appears to show the blast in the distance, followed by a rising fireball.
Killed were employees Frank Flores and Gerardo Castorena, Police Chief Art Acevedo said at a Friday evening news conference.
The Chief of the Houston Police Department, Art Acevedo, noted that while there was now no risk of health damage by inhalation, the public should still avoid inhalation exposure out of an overabundance of caution.
More from the Associated PressL "Do a search around your own home and your own neighborhood, even if you're a mile away from this location", Acevedo said.
Details about the cause of the blast were not immediately known, and there was confusion among residents.
In December, two blasts in the coastal city of Port Neches shattered windows and ripped the doors from nearby homes.
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The rain will change back to snow late Saturday into Sunday with heavy Lake Effect snow likely Sunday though Monday . New snow and sleet accumulation of less than a half inch possible, with a southwest wind around 10 miles per hour .
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The total known number of people infected now stands at 62, of which two people have died, and five are in a critical condition. For the screening, officials will check people's body temperatures and ask questions about certain symptoms, Cetron said.
"The whole ceiling fell in", a resident told KTRK about her home.
"(The explosion) knocked us all out of our bed, it was so strong", said resident Mark Brady to Click2 Houston.
The owner of the facility told Eyewitness News the explosion originated from a propylene tank.
He said: "It busted out every window in our house".
Acevedo said there is no evidence that the explosion was intentional, but they will conduct a criminal investigation as part of the process. It is highly flammable and can explode in a fire.
Jeff Linder, a meteorologist with the Harris County Flood Control District, tweeted shortly after the explosion that the rattling was gauged by radars of the area.
Houston Mayor Sylvester Turner said on Twitter said there was no hazard in the air "from all indications", but that authorities continued to monitor.
The industrial area in Houston, Texas, close to the alleged source of the large explosion in the early hours of the morning on Friday, January 24, 2020. Spring Branch ISD says they're anticipating transportation delays but otherwise are planning for a normal school day.