GREER, Arizona (CNN) -- Crews are intentionally setting fires near the Arizona and New Mexico border to control the expected spread of a massive blaze, officials said Friday.
"The fire is eventually going to get there and we want to have something to check it when it does," said Jim Whittington, spokesman for the Southwest Interagency Incident Management team. "It is likely we will pull fire across state line today."
Crews will largely focus on setting "burnout" fires in order to strategically control where the blaze goes, Whittington said. Such controlled fires remove the ground fuel in areas that feed the larger fire.
Weather conditions have helped firefighters contain the spread of the Arizona wildfire this week, but officials said factors Saturday will put conditions near critical.
"High winds, low humidity are all of the conditions necessary for large fire growth," Whittington said. "We know that the winds are going to come up on Saturday, so we have until then to get as much work done and to get to the point where we feel comfortable to where we can sit there and deal with what the winds throw at us."
Only 5% of the wildfire was contained by mid-morning Friday, officials said. The Wallow Fire has scorched more than 408,876 acres, leaving a giant bear-paw-like burn mark on the map of eastern Arizona.
The flames have also consumed 29 residences, 22 of them in the evacuated city of Greer. More than 5,200 homes are threatened, according to officials.
More than 3,000 people are working to douse the fire, from the ground and air. About 221 fire engines and 14 helicopters were in use.
Power companies said Friday that they are still watching the huge fire and its potential impact on crucial transmission lines that supply power to hundreds of thousands.
El Paso Electric said the fire is about 15 miles from lines that serve nearly 400,000 people.
The utility is working with partners and other companies on other sources of power if the lines are closed, company spokeswoman Teresa Souza told CNN. If that occurs, customers in southeastern New Mexico and El Paso, Texas, could see rolling blackouts.
Tucson Electric Power has two lines about 8 miles from the fire. Those lines carry electricity through the region to Tucson.
"We're watching it carefully," spokesman Joe Salkowski said.
If the lines are closed or damaged, the company will be able to prevent outages by using other power sources, Salkowski said.
Tucson Electric Power has a coal-powered plant about 12 miles northeast of Springerville, which is evacuated. Officials are safeguarding the plant, but its distance from the fire and the grassy terrain make it "reasonably protected," the spokesman said.
Meanwhile, authorities were discussing damage caused by the fire with residents in particularly hard-hit communities.
Authorities were notifying residents in the community of Greer, where the wildfire destroyed 22 homes and damaged five others, according to information from the Apache County Sheriff's Office posted on the InciWeb incident information site.
Officials were also notifying residents in Alpine and Nutrioso, where five homes had been destroyed, the site said. Arizona Gov. Jan Brewer declared a state of emergency earlier in the week to mobilize funds for the wildfires in Apache and Greenlee counties.
The blaze -- about the size of Houston -- has caused authorities to evacuate thousands of people since the wildfire began sweeping through the Apache National Forest on May 29.
On Thursday, Whittington, said if the blaze reached the fiber-optic cables, communication in part of Springerville would be lost. "We'll all be incommunicado."