(CNN)  -- An apparent natural gas explosion in downtown Bozeman, Montana, leveled three businesses Thursday morning, according to city and state officials.

An explosion rocks downtown Bozeman, Montana, on Thursday in a photo from iReporter Sean Gallik.

"When we say gone, we mean gone. These three businesses are gone," said Montana Gov. Brian Schweitzer, who added that the state is providing help for clean up, and to businesses and residents who are affected.

One person remained unaccounted for Thursday evening, Bozeman Assistant City Manager Chuck Winn said.

"The situation remains unsafe for anyone to enter," Winn said. "So in terms of a search -- we are unable to do so at this time."

Winn said city crews are making progress cleaning up the area, but the damage is great. He said a meeting was planned Friday morning to give business owners and residents information about when they can return.

"It literally looks like a bomb went off in downtown Bozeman," he said. iReport.com: Photos from the scene

"Roofing material, construction material is scattered for three or four blocks," he said. "It was a very violent explosion."

Schweitzer added that the situation would "not be over in 24 hours."

The blast occurred about 8:15 a.m. on the town's Main Street, Fire Chief Jason Shrauger told CNN.

The city government declared a local emergency after the blast. Initially, 11 people were reported missing, but 10 were later accounted for, Winn said.

It was not clear what triggered the blast.

Bozeman is in south-central Montana, about 100 miles southeast of the state capital, Helena.
What caused the fire? How many businesses were destroyed downtown? Where was the fire? How many people were initially reported missing after natural gas explosion? Who remains unaccounted for? Were any businesses destroyed in downtown Bozeman, Montana What triggered the blast? How many people are unaccounted for?
natural gas explosion three Bozeman, Montana, 11 One person three It was not clear One
question: What caused the fire?, answer: natural gas explosion | question: How many businesses were destroyed downtown?, answer: three | question: Where was the fire?, answer: Bozeman, Montana, | question: How many people were initially reported missing after natural gas explosion?, answer: 11 | question: Who remains unaccounted for?, answer: One person | question: Were any businesses destroyed in downtown Bozeman, Montana, answer: three | question: What triggered the blast?, answer: It was not clear | question: How many people are unaccounted for?, answer: One