FARMINGTON, Maine (AP) — A fierce propane explosion leveled a newly constructed building after fire crews arrived to investigate the smell of gas Monday morning, killing one firefighter and injuring six other people, including fellow firefighters, officials said.

The blast was so powerful it blew a vehicle across an intersection and damaged nearby buildings. Paper, insulation and building debris rained on the area.

The explosion shattered the two-story building that housed LEAP Inc., a nonprofit that serves people with cognitive and intellectual disabilities, just a couple of months after it was finished.

"It's a war zone. It's just a mess," said Scott Landry, a member of the Farmington Town Select Board. "The building is gone."

The blast injured four other firefighters, including the town's fire chief; one employee of the nonprofit center; and one ambulance worker, officials said.

The ambulance worker was treated and released, state public safety spokesman Steve McCausland said. The other five were taken to regional trauma centers and remained hospitalized. Their conditions weren't released.

The blast hit around 8:30 a.m. in this town in western Maine, about 70 miles north of Portland.

Neighbors heard a thunderous boom that rattled homes and knocked pictures off walls. Flying paper and dust made it look as if a snowstorm had hit.

LEAP worker Lisa Charles, who lives down the street from where the blast occurred, was home with her kids when the explosion startled the family.

She stepped outside to see debris falling from the sky — and feared the worst for her colleagues.

"I know everybody in there. I thought for sure everybody was gone," she said. "They got a warning from the maintenance guy who was a hero for telling them to evacuate."

Kim Hilton, who works in the admissions department at the nearby University of Maine at Farmington, said she was frightened when her building shook.

"It felt like someone hit our building with a vehicle," she said.

Gov. Janet Mills — who is from Farmington and whose office said she knew the firefighter who died — ordered flags lowered to half-staff across the state. Mills also visited the scene and promised the state fire marshal's office will investigate.

"We're going to get to the bottom of as much as we possibly can to protect this community, to protect all other communities and make sure this doesn't happen again," she told reporters.

The 40-by-60-foot building, which served as the administrative offices for LEAP, opened eight to 10 weeks ago and wasn't yet fully staffed, Landry said.

The smell of gas was detected when the first workers arrived and the building evacuated before most workers had arrived for the day, he said.

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Sharp reported from Portland.