Austen Thibault, The Union Democrat

The American Red Cross began closing its evacuation center in Sonora on Tuesday as the Tuolumne County Sheriff's Office lifted all advisory evacuations, with containment on the Rim Fire growing.

Firefighters have formed a containment line around 80 percent of the fire, which has burned 237,341 acres. The fire is still uncontained to the southeast and northeast.

Today, crews will work to contain those areas, including continued backburning. Some backburning will occur within the fire perimeter to eliminate unburned fuels.

They will also monitor the fire as it burns to the east-by-northeast rocky terrain that fire management has pushed the fire into to take advantage of the natural barrier.

Extremely dry fuels and high winds give concern for spot fires, so progress will be "slow and cautious," according a statement from the Stanislaus National Forest.

Cause investigated

While the threat of the fire diminishes, the investigation into the cause remains very active.

Tuolumne County Sheriff Jim Mele cast serious doubt Tuesday on a theory that the fire started at an illegal marijuana grow site.

"I have not received any information that anyone - fire, law enforcement or the public - found any pot evidence during the whole Rim Fire fight," Mele said, adding his office would have been informed if evidence was found.

He acknowledged, however, that Tuolumne County authorities have found marijuana gardens in the area of Lumsden Bridge in the past. The bridge crosses the Tuolumne River about five miles east of the point of origin, deep in the Clavey River canyon.

Stanislaus National Forest spokesman Jerry Snyder also cast doubt on the pot-garden theory, which was presented by Twain Harte Fire Chief Todd McNeal at a community meeting last week that was recorded and posted on YouTube and later reported by newspapers throughout the state.

"If you look at the area, it doesn't match what you'd normally want for a grow operation," Snyder said. "We're talking about a place with no roads to it - in extremely steep, difficult terrain. We couldn't even get our firefighters in there on foot it was so bad. Grow sites are typically isolated, but accessible. This is isolated and inaccessible."

Snyder noted there were no lightning strikes in that area when the fire started, eliminating weather as a possible cause.

He added falling rocks can be another natural cause of fire.

Evacuations lifted

The Tuolumne County Sheriff's Office at noon Tuesday lifted all advisory evacuations for the county.

The Red Cross subsequently began shutting down its temporary evacuation center at the Mother Lode Fairgrounds in Sonora.

At its peak on Aug. 23, the center sheltered more than 180 people, said spokesman Jordan Scott.

The shelter provided more than 950 overnight stays for evacuees and nearly 5,000 meals with the help of Mother Lode Lions Club.

More than 150 Red Cross volunteers staffed the center with the help of 50-plus area volunteers.

The evacuation center will be closed by this afternoon.

Full containment on the Rim Fire is expected Sept. 20.