AP PHOTOS: Washington blaze that killed 3 firefighters rages on; investigation underway

Firefighter Mark Groves, who said he was 32 hours into fighting fire, takes a breather Thursday, Aug. 20, 2015, in Twisp, Wash., a day after three firefighters were killed fighting a wildfire near the town. Authorities say three firefighters died after their vehicle crashed and was apparently caught by a "hellstorm" of flames as they battled a blaze in Washington state. (AP Photo/Elaine Thompson) (The Associated Press)

Firefighters prepare near an area where fire erupted in Twisp, Wash., Thursday, Aug. 20, 2015. Authorities warned that more high winds Thursday could make conditions very challenging. (Joshua Trujillo/seattlepi.com via AP) MAGS OUT; NO SALES; SEATTLE TIMES OUT; TV OUT; MANDATORY CREDIT; SEATTLE OUT (The Associated Press)

Jackson Hotshots' firefighters, from Jackson, Miss., stand with hands and helmets over their hearts as they watch a motorcade carrying the bodies of firefighters killed a day earlier while fighting a wildfire drive past Thursday, Aug. 20, 2015, in Twisp, Wash. Authorities say three firefighters died after their vehicle crashed and was apparently caught by a "hellstorm" of flames as they battled a blaze in Washington state. (AP Photo/Elaine Thompson) (The Associated Press)

An investigation was underway Thursday after a wildfire in Washington state claimed the lives of three firefighters and left four others injured, one critically.

The deaths happened Wednesday night in the scenic Methow River valley about 115 miles northeast of Seattle, where a series of blazes covering close to 140 square miles had merged.

The three firefighters were members of a specially trained unit that is sent into danger ahead of other crews to size up a wildfire. They were driving up a narrow gravel road when they crashed and flames rolled over them. The four others who were injured were nearby.

On Thursday, fire officials with notebooks and cameras walked the hills and banks near Woods Canyon Road outside the community of Twisp, investigating how the disaster happened. They provided few details, other than to say it was the blaze, not the crash, that killed the victims.

Conditions in the area were expected to deteriorate later in the day, with strong winds and high temperatures.

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