Fire investigators ask that anyone who has information about suspicious activity in the area should contact the Department of Natural Resources. The fire started Thursday on private property across Lake Chelan from the 24-Mile State Park.
As of Sunday, the fire burning on both private and Forest Service land is about 15 percent contained.
A Level 1 evacuation notice has been issued for residents of two neighborhoods in Manson, Wash., plus the Antilon Lake Campground.
Manson is about six miles from the fire.
That means people who are sensitive to smoke or have special needs should begin to make arrangements to evacuate.