Forest Service firefighters corralled a 4-acre fire Sunday evening near the Skyline Road about 10 miles north of Unity.
The blaze was human-caused, but an investigator has not pinpointed a precise cause, said Willy Crippen, fire management officer for the Burnt-Powder Fire Zone.
"We can definitively rule out lightning as the cause," Crippen said this morning.
A Forest Service engine crew that was patrolling in the area saw smoke from the blaze about 4:55 p.m. Sunday. It started near the end of the 1920-150 road near China Creek.
Two other Forest Service engines responded and the crews worked until late Sunday to build a control line around the fire.
Three engines returned today to mop up the blaze, Crippen said.
The fire spread more quickly than is typical for early June, he said.
Crews put out two other human-caused fires last week, one five miles north of Whitney, the other two miles northwest of Whitney.