Three firefighters were killed and three to four others were injured, at least one critically, on Wednesday as raging wildfires advanced on towns in north-central Washington, authorities said.

Okanogan County Sheriff Frank Rogers said the deaths, in a wildfire near Twisp, had been confirmed, but he said he was not immediately releasing further details about the circumstances. One firefighter had been taken to Harborview Medical Center in Seattle in critical condition, a nursing supervisor there said.

"My heart breaks over the loss of life," Gov. Jay Inslee said in a written statement. "I know all Washington joins me and Trudi in sending our prayers to the families of these brave firefighters. They gave their lives to protect others. It was their calling, but the loss for their families is immense."

The news came after officials urged people in the popular outdoor-recreation centers of Twisp and Wintrop, in the scenic Methow River valley about 115 miles northeast of Seattle, to evacuate as a fire near Twisp grew to about 2 square miles.

The Okanogan County Emergency Management department issued the order for the towns, which combined have a population of about 1,300.

A larger group of fires burning to the east covered about 50 square miles and prompted the evacuation of Conconully, home to about 200 people 20 miles northwest of Omak. To the south, more than 1,100 firefighters were combatting a fire that topped 108 square miles and was still threatening the resort town of Chelan.

Angela Seydel, a spokeswoman for Okanogan Emergency Management, said Wednesday evening that 4,000 homes in the region had been evacuated.

"It is really bad out there. The fires have just exploded," she said. "We're just directing everybody to head south."

A stream of cars poured south out of Twisp as dark smoke clouds loomed; the highway to the north was closed. Some people put sprinklers on their roofs in an effort to protect their homes, and others joined gas lines several cars deep.

The National Weather Service issued a red flag warning for the eastern portion of the state from 11 a.m. Wednesday to 5 p.m. Friday. Officials said temperatures will climb above 90 degrees and relative humidity will drop as low as 14 percent.

Drought and heat have combined to make this fire season of the most active in the United States in recent years. Nearly 29,000 firefighters are battling some 100 large blazes across the West, including in Idaho, Oregon, Montana, Washington and California.

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Johnson reported from Seattle. Associated Press writer Nicholas K. Geranios contributed to this story from Spokane.