A vegetation fire that broke out in Banning on Saturday forced authorities to close an 8-mile stretch of Highway 243 and the closure was expected to last overnight into Sunday.
At least 412 firefighters, two helicopters and seven air tankers were battling the blaze in steep, rugged terrain, said Melody Hendrickson, a Riverside County Fire Department spokeswoman.
The Gorgonio Fire was reported at 11:43 a.m. and charred 650 acres, officials said.
State Route 243, which connects the Inland Empire cities of Banning and Idyllwild, was closed from Poppet Flats Road to South San Gorgonio Avenue and Wesley Street.
Winds were gusting at about 20 mph.
Officials were not sure of the origin of the blaze, which burned vegetation about 9 miles north of the 3,000-acre Summit Fire, which was 85 percent contained by Saturday morning.
The Gorgonio Fire blazed over the same ground as the 41,000-acre Esperanza wildfire on Oct. 26, 2006, Riverside Fire Department Battalion Chief Mike Smith said.
Serial arsonist Raymond Lee Oyler was sentenced to death in 2009 for starting the Esperanza wildfire, which killed five firefighters.
