UPDATE: 2 brush fires burning north of Reno along US 395

RENO (AP) - Hundreds of firefighters battled a pair of brush fires Wednesday that has blackened thousands of acres on the edge of the Sierra north of Reno along U.S. Highway 395. There were no immediate reports of threats to structures.

The fires started about 2 p.m. south of Doyle, Calif., and north of California State Highway 70 near Hallelujah Junction. The Reno Gazette-Journal reported Wednesday evening that at least 600 firefighters, including federal fire crew and the Nevada Army National Guard, had been called to battle the blazes.

Heavy smoke slowed traffic, but the highways remained open, authorities said. They said the fires were believed to have been sparked by a trailer being pulled with a flat tire.

Two helicopters and a single-engine airtanker were assisting numerous hand crews, fire officials said.

Air surveillance estimated that one blaze, called the "Trailer 1 Fire," had burned 700 to 1,000 acres north and east of Hallelujah Junction, according to the Gazette-Journal. A second fire south of Doyle dubbed the "Red Rock Fire" had consumed about 2,000 acres, the newspaper reported.

Area residents appeared to be taking the fires in stride.

"We have fires up here every year," Bob Buell told KTVN-TV in Reno. "I've been here 16 years and I've never seen it without a fire this time of year."