It was a cloud of red as a helicopter dropped flame retardant on the Whittier wildfire in Santa Barbara County, California, on Tuesday.
One of the first casualties of the fire, which started last Saturday afternoon in the Los Padres National Forest, was a Boy Scouts camp. All the animals at the camp's nature centre were killed in the blaze, the park authorities said.
As of Tuesday night, the raging blaze had spread to more than 44 sq km, and about 35,000 people had been evacuated.
To combat the blaze, firefighters have been using helicopters to make air drops of water and fire retardant over the affected areas as the burning canyons are too steep for ground crews and too narrow for airplanes.
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"This topography is incredibly steep and that makes it really dangerous for our firefighters out there," Mr Lee Beyer, a public information officer for the US Forest Service, told Santa Barbara TV station KeyT TV.
Mr Mark von Tillow, a division chief at the forest service, said it could take a few weeks to fully contain the fire.
The cause of the blaze is still under investigation, but it is believed to have started from a vehicle fire.
Searing temperatures and parched land have fuelled dozens of fires in the western United States and Canada over the past week.