The U.S. Forest Service says two pilots have died of their injuries after their firefighting helicopter crashed in Idaho.

A helicopter went down in a mountainous region of Idaho while fighting an out-of-control forest fire, killing both pilots on board, officials said on Friday.

ROTAK Helicopter Services confirmed that its CH-47D Series Chinook crashed at about 3:30 p.m. local time on Thursday, battling the massive Moose Fire near Salmon, Idaho.

“There are two confirmed fatalities, which were the two pilots on board when the crash occurred,” according to a statement by Forest Service spokesman E. Wade Muehlhof.

The Forest Service identified the victims as 41 year old Thomas Hayes from Post Falls, 36 year old Idaho, and Jared Bird from Anchorage, Alaska.

The wreckage was quickly found and the pilots rushed to a hospital, ROTAK Helicopter Services General Manager Ely Woods told BBC News on Friday.

Woods called the operators "two very experienced" pilots.

We're working to figure out a reason" why the craft crashed, Woods said.

As of Friday morning, at least 23,620 acres had been burned as 690 firefighters battled the blaze and scorching heat with the mercury expected to hit 91 degrees later in the afternoon.

The fire was ignited on Sunday afternoon at about 4 p.m., 21 miles north of Salmon. Firefighters said they don't believe the blaze will be contained until late August.