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An explosion at a northwest Houston manufacturing business shook part of the city early Friday, sending at least one person to a hospital, damaging nearby homes and sending firefighters scrambling to put out a resulting fire.

At least one person is unaccounted for after the blast at Watson Grinding and Manufacturing, Houston Police Chief Art Acevedo said.

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.

A fireball apparently rose from the scene after the blast, video posted to Twitter shows. The distant footage was taken by a camera mounted to a home window.

Debris flew a half-mile from the explosion site, Acevedo tweeted.

Details about what caused the explosion weren’t immediately available. At least one person was injured by shattered glass and was taken to a hospital, Houston fire Capt. Oscar Garcia said.

Many homes in the area were damaged, including broken windows and doors, and in at least one case, a collapsed ceiling, CNN affiliates reported.

“The whole ceiling fell in,” a resident told KTRK about her home.

“I thought maybe the house had gotten hit by lightning. And then I realized there was no storm,” the resident told KTRK. “No one can figure out what happened.”

Mark Brady, who lives about a half-mile from the manufacturing business, told CNN affiliate KPRC the blast “knocked us all out of our bed.”

“It busted out every window in our house. It busted everybody’s garage door in around here … and closer toward the explosion over here, it busted people’s roofs in and walls in.”

More than an hour after the explosion, aerial video from KTRK showed smoke and flames rising from the blast site.

Small explosions followed the first blast

Small explosions happened at the site in the first few hours after the massive blast, Acevedo said.

No evacuations were immediately ordered, Harris County Sheriff Ed Gonzalez said on Twitter around 6 a.m. CT.

“First responders are checking on residents immediately adjacent to the facility. Firefighters continue to try to put out the flames,” Gonzalez wrote.

A school district in the area, Spring Branch ISD, said it plans for a full school day, though buses may be delayed.

“We will keep all students inside today as air quality in the area continues to be monitored,” the district said on Twitter.