Firefighters Friday were trying to make progress after the Canyon fire exploded to nearly 5,000 acres, forcing residents in northern Los Angeles and Ventura counties to evacuate.

Fire crews from Ventura and Los Angeles counties are battling a rapidly growing vegetation fire in Holser Canyon, near Lake Piru, in 100-degree heat. The blaze, called the Canyon Fire, is estimated to be at 1,

Andrew Dowd, the spokesman with the Ventura County Fire Department, said an estimated 150 to 200 firefighters were on the scene. “We’re doing a significant initial attack,” Mr. Dowd said.