Pomeroy, Wash. ? Residents of at least 150 homes in southeastern Washington were forced to evacuate as a fire that had charred as much as 27,000 acres moved north out of the Umatilla National Forest onto private land.

Farmers beyond the flames were plowing up broad swaths of earth through fields of wheat and other crops, trying to create breaks to save this year’s harvest, said Marc Hollen, spokesman for the Northwest Fire Coordination Center in Portland, Ore.

The leading edge of the fire, which had covered just 150 acres on Saturday morning, was about 10 miles south of this rural community, authorities said Sunday.

“At the moment it’s zero percent contained, burning vigorously in timber, grass and brush,” said John Townsley, also of the Northwest Fire Coordination Center.

A thick layer of smoke over the region grounded water tankers and helicopters for much of the day. There were no reports of injuries, but three structures have burned, officials said. It could not be immediately determined whether the structures were houses or sheds.

The cause of the fire was not yet known. No lightning strikes were reported in the area Friday, when it started in tinder-dry conditions.