T he enormous Rim Fire in and around Yosemite National Park in California is 80 percent contained after a few days of favorable weather allowed firefighters to make progress against the flames, which have already burned almost 370 square miles and destroyed 11 houses. Sheriff’s offices in Tuolumne and Mariposa counties have lifted evacuation advisories for the towns that the fire had been threatening.

The cause of the fire is still under investigation. Last month, a local fire chief speculated that the fire might have started at an illegal marijuana farm, saying that the conflagration began in a remote, inaccessible location. Other officials cautioned that determining the cause will take a long time:

Chief Todd McNeal of the Twain Harte Fire Department told a community group recently that there was no lightning in the area, so the fire must have been caused by humans.

“We don’t know the exact cause,” he said in a talk that was posted Aug. 23 on YouTube. “Highly suspect it might have been some sort of illicit grove, a marijuana-grow-type thing, but it doesn’t really matter at this point.”

The video was first reported Saturday by the San Jose Mercury News.

Officials overseeing the fire suppression effort would not comment on the statement and would only say that the cause is still under investigation.

“There has been some progress but there are no additional details at this time,” said Rena Escobedo, a spokeswoman with the Rim Fire incident command team. The U.S. Forest Service is leading the investigation.

McNeal could not be reached for comment Tuesday.

Whether a marijuana grow or something else was the cause of the fire will take a long time to determine, said Doug Allen, a retired division chief in charge of law enforcement for the California Department of Forestry and Fire Protection in Southern California.

Allen said investigators generally follow char marks on trees and rocks to help find the fire’s point of origin, then mark off the territory into grids that are searched for clues. A lightning strike, for example, might have melted sand into glass.

“Everything will have carbon stains that will tell them which direction it came from,” Allen said. “You won’t find the point of origin on every fire. Maybe a bulldozer has driven over where it started and you’re out of luck.”

Illegal marijuana grows in national parks and forests have tormented federal land managers for years. Growers hike into remote canyons with poisons and irrigation lines and set up camp for months. The poisons kill wildlife and seep into streams and creeks. The growers leave tons of garbage behind.

Associated Press

Due to winds, heat, and mountainous terrain, firefighters had a hard time containing the fire for about two weeks. Recently, conditions began to change in their favor:

First, lines that they built with bulldozers, shovels and chain saws for miles around the fire in Stanislaus National Forest, where the blaze began Aug. 17, have checked its spread and spared towns on the northern edge, such as Twain Harte, Tuolumne City and other communities along Highway 108 east of Sonora.

Second, the weather cooled somewhat over Labor Day, and winds have not picked up.

And third, once it reached the park, the fire’s spread has been limited by the landscape. Lakes, such as Hetch Hetchy Reservoir and Cherry Lake, and high-altitude terrain, which has significant amounts of granite and smaller trees, have not provided as much fuel to burn, and some parts of the fire have reached sections of the park where controlled burns were done in the past decade to limit overgrown conditions.

San Jose Mercury News

Authorities expect the fire to be fully contained by Sept. 20, although it will continue to burn for some time. For the most recent official information on the fire, continue reading here.