Just as firefighters were getting a handle on one large blaze north of Los Angeles, a new wildfire ignited roughly 50 miles to the west, spreading across nearly 800 acres.

The latest fire, in Riverside County (search), forced road closures as it briefly threatened several homes, said Rick Griggs, a county fire engineer. The fire was 50 percent contained late Thursday night, and firefighters hoped to have it surrounded by Friday morning.

It erupted Thursday in brush and grass along hills near the community of Fairview, but winds were slow and accessible terrain allowed use of bulldozers to dig lines. "We're getting some pretty good cooperation from the weather," Griggs said.

Three of the more than 400 firefighters battling the blaze suffered injuries. One was treated at a hospital for moderate burns to the face and the other two suffered heat exhaustion.

Meanwhile, firefighters were being released from the lines at a fire at the edge of the Mojave Desert (search) in northern Los Angeles County. The 11,816-acre blaze destroyed two homes and a historic wood bridge, but was 80 percent contained.

About 2,400 firefighters battled the human-caused fire. Eight people suffered minor injuries.

Earlier in the week, firefighters fully contained the two fires in northern Los Angeles County.

Los Angeles County Fire Inspector Mike McCormick said Thursday that the early series of blazes indicates "we've got a long summer ahead of us."

"These are the conditions: hot, dry, low humidity and windy," he said. "So we'll just try to get some rest then go out and do it again."

In Alaska, seven firefighters were hurt Thursday when a tracked vehicle rolled as it transported a crew to a more than 485,000-acre fire north of Fairbanks. Four were taken to a hospital by helicopter and three others were taken by ground transport; five of those were released.