A massive wildfire that has claimed more than 30 homes and forced nearly than 10,000 people to evacuate is likely to spread into New Mexico soon, authorities said, threatening more towns and possibly endangering two major power lines that bring electricity from Arizona to West Texas.

The fire has now burned 639 square miles (1,655 sq. kilometres) of forest, an increase of 114 square miles (295 sq. kilometres) from a day earlier, officials said on Friday.

Lighter winds Thursday and Friday have helped the 3,000 fire-fighters on the lines make progress, but critical fire conditions remain, said Jim Whittington, a spokesman for the teams battling the fire. High winds are expected to return with a vengeance on Saturday.

“We have until then to get as much work as we can done and get to the point where we can sit back and watch the winds come and do what we have to then,” Whittington said.

Fire crews plan to try to strengthen what lines they’ve been able to establish and continue burning out forested areas in front of the main fire to try to stop its advance. It was officially just 5 percent contained Friday, but the actual numbers are likely higher, Whittington said.

The advances came on the north side of the fire, near two large towns at the edge of the forest that have been evacuated.

The two Arizona-Texas power lines are still in the path of the fire, although Whittington said he was less concerned about them Friday. El Paso Electric has warned its 372,000 customers that they may face rolling blackouts if the lines are cut.

The blaze in the Apache-Sitgreaves National Forest has destroyed 31 homes or cabins, including 22 in the picturesque mountain community of Greer, Whittington said. Two dozen outbuildings and a truck were also lost and five homes damaged in Greer when the fire moved in Wednesday night.

A DC-10 tanker made three retardant drops near the community Thursday, and officials hope that by Saturday the threat will be much less.

Nearly 10,000 people have been evacuated from the towns of Springerville and Eagar on the edge of the forest and several mountain communities in the forest itself.

“I can’t even speculate on when we can let people back in, but I can tell you we’re not going to let people back in until we can be sure they will be safe and don’t have to leave again,” Whittington said.

Much of the growth toward New Mexico has actually been from fires started by fire-fighters trying to burn out fuels ahead of the blaze so it can be stopped, Whittington said. That technique allows the fires to be controlled and less hot. But there is little doubt it will cross the border, he said.

The fire doesn’t appear to have moved into New Mexico yet, said Catron County Undersheriff Ian Fletcher. He said fire crews were cutting down trees and burning fuels along U.S. 180 near the Arizona border.

Both Luna and the county seat of Reserve were being powered by a large generator because of worries that electricity to the area would be cut, Fletcher said.

Authorities suspect the 408,876-acre (165,469-hectare) fire was sparked by a campfire. It is the second-largest wildfire in state history.

The fire has rekindled the blame game surrounding ponderosa pine forests that have become dangerously overgrown after a century of fire suppression.

Some critics put the responsibility on environmentalists for lawsuits that have cut back on logging. Others blame overzealous firefighters for altering the natural cycle of lightning-sparked fires that once cleared the forest floor.

More In: International | News