Already waging a furious battle against wildfires, heavy-hearted investigators on Thursday will try to figure out what caused a vehicle crash that cost three firefighters their lives in Washington state.

The three firefighters, who worked for the U.S. Forest Service, were trying to control a blaze that broke out Wednesday afternoon and spread quickly and erratically, driven by wind and feeding on drought-parched land.

They were killed near the tiny town of Twisp, about 30 miles south of the Canadian border, which was quickly evacuated.

The three firefighters were not immediately identified. Authorities said fire apparently overtook the crashed vehicle, but there was no further word on what happened or what equipment the firefighters had to protect them from the fast-moving flames.

Sheriff Frank Rogers of Okanogan County told KXLY-TV: “It was a hellstorm up there. The fire was racing, and the winds were blowing in every direction.”

Four other firefighters were injured, one critically, though it was not clear whether those four were linked to the three dead.

Image: Twisp, Wash. fire

Image: Twisp, Wash. fire

President Barack Obama offered thoughts and prayers “on behalf of a grateful nation,” and Gov. Jay Inslee said he was heartbroken.

“They gave their lives to protect others,” he said. “It was their calling, but the loss for their families is immense.”

Almost 30,000 firefighters from all over the country are battling about 100 wildfires that have broken out across the West. The flames have torched more than 1 million acres of land.

The fire that killed the three firefighters began on about 50 acres, eight miles outside Twisp, a town of 900 people. It quickly grew to 1,500 acres, the state Department of Natural Resources said.

It was separate from a nearby fire known as the Okanogan Complex, which grew to almost 31,000 acres with only 20 percent containment. Winds were expected to grow on Thursday and Friday, increasing the danger.

And five other blazes, collectively known as the Chelan Complex, had reached almost 70,000 acres on the eastern edge of Okanogan-Wenatchee National Forest, only about 50 percent contained.