Eight emergency responders were transported to Mat-Su Regional Medical Center after controlling a hangar fire near Butte that damaged three aircraft.
They were evaluated for symptoms resulting from smoke inhalation after a blaze started during the early hours of Tuesday.
One of the responders was still being evaluated Tuesday afternoon, according to borough spokesperson Patty Sullivan.
The fire burned for three hours and damaged three aircraft, Mat-Su Borough officials said.
According to Sullivan, a private hangar located on the 17900 block of East Maud Road caught fire around 2 a.m.
Palmer Fire Department Chief John McNutt, the incident commander, said the owner received a phone alert that his fire alarm system was malfunctioning and that he quickly realized the building was on fire once he got on site.
All three of the damaged aircraft were small planes, roughly the size of a Piper Super Cub, and equipped with wheels rather than floats. They are owned by the same individual who reported the fire at the 66-foot-by-66-foot hangar.
None of the airplanes appear salvageable, McNutt said.
Four of the responders transported to a hospital were firefighters from Palmer, four were firefighters from Butte and one was a medic.
Two were monitored and released around noon, and one was still being monitored Tuesday evening.
According to McNutt, a total of 18 volunteer responders arrived to extinguish the fire. Less than 3,000 gallons of water were used to bring the blaze under control.
The weather and low temperatures made the task more difficult, McNutt said.
The cause of the fire is being investigated by the state fire marshal, who visited the scene and will take several days to compile a report.
While the aircraft themselves have been ruled out as the cause of the fire, McNutt said the hangar's owner was building an upstairs room inside the building.
Channel 2's Samantha Angaiak contributed to this story