Investigators searching for answers into what caused the massive wildfire burning in and around Yosemite National Park have made some headway, fire officials said Friday.

Most authorities are mum about the details, but one fire official in Tuolumne County offered a tantalizing clue when he recently told a community meeting that the fire was likely caused by marijuana growers.

“We don’t know the exact cause,” said Todd McNeal, fire chief in Twain Harte, a town that has been in the path of the flames. But he told a community meeting that it was “highly suspect that there might have been some sort of illicit grove, a marijuana-grow-type thing.”

“We know it’s human caused. There was no lightning in the area,” said McNeal, a former captain with the Sonora Fire Department who has fought fires for 23 years for the Forest Service, the National Park Service and other agencies in the Sierra Nevada.

His remarks, made on Aug. 23, were recorded and posted on YouTube in a video that has gotten surprisingly little attention.

Officially, authorities were saying little.

“The cause is still under investigation. There has been progress in the case, but we can’t share any additional details at this time,” said Stanton Florea, a spokesman with the U.S. Forest Service.

The Rim Fire began Aug. 17 in a remote area of Stanislaus National Forest called Jawbone Ridge, far from any paved road. Smoke from the blaze has drifted so far that satellites are measuring it thousands of miles away over Canada and the Great Lakes — and in traces over Europe.

By Friday, the fire had burned 213,414 acres, making it the fifth largest wildfire in California history. It was 35 percent contained; fire officials are estimating full containment on Sept. 20.

Over the past decade, the Forest Service and rural police have reported an increasing number of huge marijuana plantations being found in national forests across California and other states. The operations are run by Mexican drug cartels and are often guarded by armed lookouts, authorities say.

The growers have shot wildlife, rerouted streams and poisoned parks and forests with pesticides. They also have started fires.

In 2009, a huge fire that burned 90,000 acres in the Los Padres National Forest near Santa Barbara was set by a campfire from an illegal marijuana grow, Forest Service investigators concluded at the time. The Santa Barbara County Sheriff’s Department said the operation was run by a Mexican drug cartel. Deputies reported finding 30,000 marijuana plants and an AK-47 assault rifle in a remote canyon near where the wildfire started. They also found piles of garbage, propane tanks and a charred stove.

A few weeks after that incident, the Santa Barbara County sheriff said that the tightening of security around the U.S.-Mexico border had led to the rise in drug gangs deciding to grow marijuana on public lands in California.

“It’s made it much more difficult for the cartels to smuggle into the country, particularly marijuana, which is large and bulky,” Sheriff Bill Brown said. “It’s easier to grow it here.”

McNeal, the Twain Harte fire chief, did not return calls on Friday, as 5,000 firefighters continued to battle the flames.

A top political leader in the area said that marijuana growers have been an ongoing problem in Stanislaus National Forest.

“We know that these illegal pot growers are out in our forests, and I think this fire just wiped out a whole bunch of them,” said Randy Hanvelt, chairman of the Tuolumne County Board of Supervisors.

“It’s a problem in all the Sierra forests,” he added. “When we find them, we pull out like 20,000 plants at a time.”

Hanvelt said he did not know what leads Forest Service investigators have made in cracking the case. The area where the fire started is roughly 10 miles west of the Yosemite National Park entrance on Highway 120 and 8 miles east of the town of Groveland — a rugged, steep expanse of dense wilderness.

“It’s a tough place to get to,” he said. “You don’t get there by accident.”

In June, deputies pulled out 15,000 marijuana plants from the adjacent forest to the south, Sierra National Forest. The Madera County Sheriff’s Department removed four miles of irrigation pipe connected to streams and more than 2,000 pounds of garbage, propane tanks, bedding and food. A month earlier, fire crews battled a 40-acre wildfire in the same area, and authorities said it had been set by marijuana growers tied to Mexican drug cartels.

Also Friday, U.S. government satellites continued to churn out images showing just how far the Rim Fire’s impacts are being felt.

Smoke from the blaze drifted at least 2,500 miles, and reached Michigan, Indiana, Ohio and the Great Lakes. The soot particles, picked up by nine weather satellites run by NASA and the National Oceanic and Atmospheric Administration, were 10,000 feet or higher in the air, however, and weren’t affecting air quality in most places, except areas near the fire, such as Reno and the San Joaquin Valley.

Mark Ruminski, a meteorologist with NOAA’s satellite analysis division in College Park, Md., said that European satellites have even detected low levels of soot from the fire over Scandinavia. The particles will disperse and wash out of the atmosphere after it rains, he said.

“Sometimes people will say ‘I can smell smoke,’ but most of the time if you are a thousand miles away you don’t even know it,” he said.