Craig Cassidy, The Union Democrat

The Labor Day weekend will be no holiday for the nearly 5,000 firefighters and support personnel battling the Rim Fire in southern Tuolumne and northern Mariposa counties.

Fire-suppression work on the 201,894 acre blaze will continue today and carry through Monday, according to U.S. Forest Service officials.

The work is occurring on all flanks of the fire, and entails direct fire suppression, construction of backup lines and, weather permitting, back burning operations.

"We won't take any time off on this thing - we can't," said Forest Service spokesman Dick Fleishman at the incident command center outside Groveland.

"They will be working on containment on all sides … just continuing to get around this thing."

As of this morning, 4,931 people and several aircraft were assigned to the fire. It was 32 percent contained.

Warmer, dryer weather could slow progress in coming days, Fleishman said.

"Good progress" was made Thursday along the western flank, an area threatening communities south and east of Highway 108.

However, at this time, the fire is burning most actively in the south and east, along Pilot Ridge in Mariposa County and in Yosemite National Park.

Acting Gov. Darrell Steinberg on Thursday declared a state of emergency for Mariposa County, on behalf of Gov. Jerry Brown, who was out of state.

Brown earlier declared states of emergency in Tuolumne County and for San Francisco, which relies on the Hetch Hetchy system for water and power.

Several homes are threatened in Mariposa County. Areas south of Highway 120 have been evacuated.

The Tuolumne County Sheriff's Office lifted evacuation advisories late Thursday for Tuolumne City, Soulsbyville, and Willow Springs - an indicator of progress on the fire's western front.

The advisory remains in effect for Ponderosa Hills and areas east, south of Highway 108 up to Pinecrest.

The fire is now burning most actively in the south. An evacuation order remains in effect for areas south of Highway 120 near Yosemite.

The Rim Fire is expected to be fully surrounded by Sept. 20. While mop-up operations in some areas have already started, the fire is not expected to be fully extinguished until winter rains and snow arrive.

The fire started Aug. 17 in the Clavey River Canyon.

Its cause remains under investigation.

U.S. Forest Service investigators yesterday returned to the area where the fire started, a steep and remote hillside on the south slope of the river canyon, about five miles west of the Lumsden Bridge, said Forest Service spokesman Jerry Snyder.