A fast-moving wildfire burned 40 homes across about 23 square miles of central Washington grassland, timber and sagebrush, a fire spokesman said Tuesday.

Fire commanders estimate the blaze has burned at least 15,000 acres since it started Monday afternoon east of the town of Cle Elum, said Mark Grassel, a state Department of Natural Resources spokesman.

Fire officials said more homes were threatened. So far, no injuries have been reported.

The fire crept within six miles of Ellensburg, Grassel said. Crews stopped its forward movement, although it is not contained. State officials dispatched additional firefighters and equipment to the blaze from around the state.

The Kittitas County sheriff's office warned those in the fire's path to evacuate. Few people took advantage of an emergency shelter in Cle Elum.

The fire also threatened a chimpanzee sanctuary, KING-TV reported. It burned some property but the chimps were OK, Diana Goodrich of Chimpanzee Sanctuary Northwest told the station.

The state Transportation Department said a 14-mile section of U.S. Highway 97 was closed because of the fire.

The fire started along Highway 10 between Ellensburg and Cle Elum, said Kent Verbeck, a commissioner and one of the volunteers with Fire District 7.

"It went on up the hillside in an area where there are some pretty nice homes and it burned up there," Verbeck said. "There may be cabins and outbuildings as well."

Verbeck was on the fire line until early Tuesday.

"A lot of the area is sagebrush, which is really dry and burning with a pretty good flame," he said. "Lot of dry terrain with the wind going the right way and it just kept going," Verbeck said.

"It eventually got so big and spread so much late last night we were dealing with miles of fire front," he said.