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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