Fire crews in several Western states struggled in forests and on rugged hillsides to tame a batch of lightning-caused wildfires while new thunderstorms threatened.

Since the weekend, more than 50,000 acres have been scorched, dozens of structures have been destroyed and several firefighters have been injured in fires from Southern California to Canada. The National Weather Service said there was a chance of more thunderstorms through Saturday.Two wildfires near Kelso, Wash., forced the evacuation Wednesday night of about 250 homes. No structural damage or injuries were reported, but the fires burned about 30 acres of wooded, hilly land.

In Southern California, a late-afternoon storm brought fierce winds that rekindled a 7,000-acre fire burning near homes in Orange County's Santiago Canyon.

The blaze, started by lightning Monday, roared back to life as wind-swept embers leapt a road that had served as a firebreak. No building damage or serious injuries were reported, and the fire was 70 percent contained late Wednesday.

Lightning strikes also sparked more than a dozen new blazes in other California counties. Most were quickly contained, however, as the storms blew through in a matter of hours. By nightfall, skies had cleared and the 60-mph winds had calmed.

The West's most destructive fire was in the Juniper Flats area of Riverside County, 85 miles southeast of downtown Los Angeles. A 6,000-acre blaze this week destroyed 73 buildings, including 44 dwellings, most of them mobile homes. Damage was estimated to be $4.5 million.

That fire was 90 percent contained and firefighters expected to completely stop it from spreading Thursday, said Joanne Evans, a California Department of Forestry spokeswoman.