The blast on Monday morning killed one firefighter and injured six other people, including fellow firefighters, officials say.

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-storey building that housed LEAP, 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 centre; and one ambulance worker, officials said.

The blast hit around 8.30am in this town in western Maine, about 110km north of Portland.

Neighbours 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.

Australian Associated Press