Hot, windy conditions threatened to cause more problems Tuesday for firefighters struggling to contain a wildfire bearing down on hundreds of evacuated homes.

State Forester Bill Crapser said the blaze had covered 4,500 acres, or 7 square miles, in an area about 5 miles south of Casper, Wyoming's second-largest city.

Wind up to 30 mph was forecast in the area, Crapser said. "We're starting to see some pretty extreme fire behavior," he said.

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Authorities had ordered the evacuation of several subdivisions on Casper Mountain, which together hold hundreds of homes, said Rick Young, spokesman for the Natrona County Fire Protection District. He said flames were within a couple hundred yards of homes in one subdivision.

The fire began Monday morning and spread quickly in grass and pine forest. One cabin and a truck burned but no injuries were reported.

Elsewhere, cooler air helped firefighters in Southern California advance on a blaze that charred about 7 1/2 square miles of hillside brush and temporarily cut power in northern Los Angeles County on Sunday. Germain Aguilara, spokesman for the Los Angeles County Fire Department, said they hoped to have the fire fully contained by Wednesday night.

"The crew keeps advancing on it," Aguilara said. "As long as the wind out there is not erratic, that will help us make progress."

In Washington state, about 550 Army soldiers were being sent to fires that had blackened more than 140 square miles in the Okanogan and Wenatchee national forests.

More than 2,285 firefighters had been assigned to the fires, blamed on lightning strikes in July.

In Idaho, a blaze in the Salmon-Challis National Forest, 7 miles north of Stanley, had grown to more than 25 square miles and was threatening vacation cabins. It was being fought by more than 700 firefighters.

Lightning in northern Nevada also started 10 brush fires in Elko County along a 100-mile stretch from Interstate 80 to near the Idaho line, authorities said Tuesday. Five firefighters were treated after their truck overturned, but the most serious injury was a broken arm, authorities said.