More accurate mapping allowed fire officials to downsize their estimate of the Fischer fire from 500 acres to 375 acres on Tuesday evening, according to Robin DeMario, spokeswoman for the Okanogan and Wenatchee National Forests.

About 500 firefighters were assigned to the fire, which was burning on private, state and national forest land. No structures have burned, and fire activity had diminished significantly, DeMario said.

For that reason, residents of the 38 homes evacuated in the Derby and Williams Canyons areas were to be allowed to return home Wednesday morning, she said.

Authorities announced Tuesday the fire was believed to be human caused. Investigators were following several leads, said Elton Thomas, fire management officer for the Okanogan and Wenatchee National Forests.

Witnesses said they saw motorcycles on a hillside right before the fire started at about 7 p.m. Sunday. Fire information officer Penny Hulse said investigators were looking at several possibilities, including whether motorcyclists may have been to blame.

About 20 miles northwest of Yakima, the Mud Lake fire was estimated at about 1,300 acres Tuesday. No homes were evacuated, and no structures had burned.

The fire was believed to have started Monday afternoon when a telephone repair truck struck a power line, said Dave Kvamme, spokesman for Pacific Power. The contact may have created an electrical surge in the line, which caused a damaged line elsewhere to fail, igniting the fire, he said.

About 975 people had been without power as a result, but crews were able to restore electricity at midnight Monday with the help of firefighters, Kvamme said.

Near Lake Chelan, firefighters continued to monitor a complex of three fires that have been burning for weeks. The Pot Peak-Sisi Ridge complex remained at 46,970 acres and was 85 percent contained.

About 485 firefighters were assigned to the three fires.

All three fires in the complex were started by lightning - the Pot Peak fire on June 26 and the Deep Harbor and Sisi Ridge fires on July 19. The Deep Harbor fire burned a dock and picnic shelter at a campground.

The cost of fighting the three fires stands at more than $19 million.

Eighty firefighters were assigned to the Rattlesnake Peak fire about 40 miles west of Yakima. The lightning-caused fire has burned about 730 acres in an area that had not burned for 60 years.