Authorities are offering a $500,000 (€393,000) reward for the arrest of the arsonist responsible for the deaths of four firefighters in America’s worst tragedy of its kind in five years.
A fifth firefighter was in a grave condition with burns over 90% of his body.
Firefighters battled through thick smoke as curtains of wind-whipped orange flame pushed through uninhabited brushland about 90 miles east of Los Angeles.
The blaze that broke out in southern California on Thursday destroyed homes, forced 700 people to flee, and flushed coyotes and other wildlife into the open.
Investigators have not said how they know the nearly 40-square-mile blaze was arson, how it was set, or why. But they said those responsible could face murder charges.
Two young men were seen leaving the area where the fire broke out about 1am (9am Irish time) on Thursday. Also, investigators said they were looking into whether the wildfire was related to other blazes in recent months, including a canyon fire last weekend.
More than 1,700 firefighters worked to contain the advancing flames. Mop-up work was under way back in the mountain communities where the flames swept through the previous day. About 400 people remained evacuated last night.
The US Forest Service firefighters were killed on Thursday when the wind blew a wall of flames down on them in the hills near Palm Springs as they tried to protect a home.
It was the worst disaster involving firefighters battling a wildfire since 2001, when four firefighters were trapped by flames and killed in Washington state.
Governor Arnold Schwarzenegger added $100,000 (€78,000) in state money to a reward already posted by Riverside County for information leading to the arsonist.
The US Forest Service and the California Department of Forestry were also investigating the firefighters’ deaths, gathering information on weather, topography and fuel. They interviewed firefighters who were nearby and retrieved information from dispatch tapes.
Michael Wakowski, a fire division chief in the San Bernardino National Forest, said it did not appear the crew did anything wrong.
“Sometimes things go bad, I hate to say,” he said.