SPRINGERVILLE, Ariz. - A raging forest fire in eastern Arizona that has forced thousands from their homes headed Wednesday for a pair of transmission lines that supply electricity to hundreds of thousands of people as far east as Texas.

The 607-square-mile blaze is expected to reach the power lines as early as Friday. If the lines are damaged, parts of New Mexico and Texas could face rolling blackouts.

Firefighters who have helped keep the flames away from several towns in eastern Arizona were concerned that high winds could carry embers that can cause new, smaller spot fires.

"We have a lot of people out there who are going to be doing nothing but looking for spots and putting those things out if they see them," fire information officer Jim Whittington said.

The blaze has blackened about 389,000 acres and destroyed 11 buildings, primarily in the Apache-Sitgreaves National Forest. No serious injuries have been reported.

Fire crews had furiously worked to protect the towns of Eagar and Springerville on Tuesday, and it appeared to pay off. They created barriers between the towns and the fire and burned out combustible material.

"It's looking good to us," Apache County Sheriff's Office Chief Deputy Brannon Eagar said. "It did what the team said it would do when it came over the hill toward town."

The fire prompted Texas-based El Paso Electric to issue warnings of possible power interruptions for its customers in southern New Mexico and West Texas.

The company uses two high-voltage lines to bring electricity from the Palo Verde Nuclear Generating Station west of Phoenix to the two states. Losing the lines would cut off about 40 percent of the utility's supply, possibly triggering the rolling blackouts among its 372,000 customers.

Winds in the area were expected to gust up to 35 m.p.h. Officials in Catron County, N.M., told residents of Luna to be prepared to leave if winds push the blaze into western New Mexico.

About half of the 4,000 residents who call Eagar home were forced to leave Tuesday as fire licked the nearby ridges. Those in neighboring Springerville worried as they awaited word of whether they would have to flee.

On Wednesday afternoon, authorities ordered more evacuations as the wildfire pushed closer to Eagar and Springerville.

The evacuation area did not contain a lot of homes, but the airport and a grocery store are located there.

About half of Eagar was ordered evacuated Tuesday, but this is the first order that affects nearby Springerville. Most of that town's residents are not affected.

The blaze, burning in mainly ponderosa pine forest, was sparked May 29 by what authorities believe was an unattended campfire. It became the second largest in Arizona history Tuesday.