Willimantic fire officials say one person is in critical condition after an apartment fire Sunday night.

The fire broke out just before 10 p.m. at the Armory Apartments on Pleasant Street. Fire crews received several 911 calls reporting the blaze, as well as a notification from the building’s fire alarms.

Willimantic fire crews arrived minutes later and found smoke and fire coming from the back of the building. Officials said one person was out of the building and was injured.

The Willimantic Police Department assisted in evacuating other residents from the apartments. The resident who was injured was taken to Hartford Hospital for serious burn injuries and then transferred to the Bridgeport Hospital burn center, according to officials.

Crews tackled the fire, which also extended to the second-floor apartment and into the attic. The fire was escalated to a second alarm for additional mutual aid.

Officials said the snow made the roads “less than ideal” for reaching the scene.

After crews worked to open ceilings and walls, the flames were visible through ventilation openings in the room, and a third alarm was raised for additional resources. Willimantic fire crews were assisted by other fire departments from North Windham, Windham Center, Windham Hospital paramedics, Mansfield, University of Connecticut, Columbia, Coventry, Hebron, Scotland, and Norwich.

The fire was eventually brought under control and fully extinguished.

“I’m proud of [the fire crews’] efforts and grateful to our mutual aid partners for their assistance in helping us bring this incident under control,” Fire Chief Ron Palmer, Jr., said.

The building once served as a state armory and was renovated years prior into a 30-unit apartment, officials said. Six apartments were affected by fire, smoke, or water damage and have been ruled uninhabitable.

The Windham Fire Marshal’s office, along with the Connecticut State Police Fire Explosion Investigation Unit, will be investigating the cause of the fire.