Investigators said Tuesday they believe marijuana growers with possible ties to Mexican drug cartels caused an 88,650-acre wildfire in northern Santa Barbara County, and there are many more pot farms hidden in remote areas around the nation.

"No pun intended, it's a growing problem," U.S. Forest Service Special Agent Russ Arthur said.

Arthur said an unspecified "cooking device" left at an encampment by suspected drug traffickers sparked the blaze on Aug. 8 that has scorched more than 137 square miles of brush and timber and briefly threatened two dozen ranches and homes.

About 30,000 marijuana plants and an AK-47 assault rifle were found near the origin of the blaze in a remote canyon in Los Padres National Forest, authorities said at a news conference. Arthur said the plants' quality is similar to marijuana linked to Mexican drug cartels, though he acknowledged the investigation into the link was ongoing.

"The type of location, the remoteness, the situation of the encampment, the type of plants, the quality ... it fits the same M.O. as all the others we've worked," around the nation, Arthur said.

Fire crews were making progress against the fire on Tuesday, and it was 75 percent contained.

Farther north, a blaze in the Santa Cruz Mountains was 80 percent surrounded. All but about 20 of some 2,200 evacuees had been allowed back home by Sunday. The fire has burned more than 7,100 acres, or about 11.2 square miles.

Some evacuation orders also have been lifted in the Sierra Nevada foothills, where a wildfire has charred more than 3,500 acres, or 5.6 square miles. The fire, which destroyed two homes when it first broke out Friday, is now 30 percent contained.

The Santa Barbara County wildfire was the first in county history to have been caused by drug traffickers but such operations typically cause three to four smaller blazes in California each year, Arthur said.

Investigators said it's believed the number of clandestine marijuana farms in the United States is rising as international drug cartels turn to public lands.

"We have evidence that most of these types of marijuana grows are the work of drug organizations out of Mexico," Santa Barbara County Sheriff Bob Brown said. "The profits that are earned through the sales of the marijuana grows are pumped back to the drug cartels and they use the money to fuel the violence south of the border."

Tens of thousands of marijuana plants have been seized in recent weeks as federal, state and local officials stage annual harvest-season sweeps for clandestine farms.

In Santa Barbara County alone, sheriff's investigators have recovered more than 225,000 pot plants in the past five months, Brown said. The plants have an estimated street value of about $675 million.

In the Sierra Nevada, an ongoing search has resulted in dozens of prosecutions and the destruction of more than 400,000 marijuana plants.

The campsite associated with the fire was at the bottom of a canyon slope that was being used for pot production, authorities said. The 2- to 6-foot-tall plants were not burned in the fire but were later pulled up and destroyed by authorities.

Officials showed a photograph of the makeshift campsite where burnt cans and pots littered the ground. A propane tank also was found, authorities said.

As many as six people were believed to have been at the camp, authorities said. No one has been arrested but some of those who fled the camp may still be in the forest, authorities said.

Some of the people staying at the encampment apparently returned several days after the fire began, authorities said.

There have been 100 arrests of suspected growers and traffickers in California this year, most of them involving Mexican nationals.

But Brown said no arrests have been made in Santa Barbara County. Most traffickers manage to flee at the first sign of trouble, he said.

"They can hear when we are coming," Brown said. "They are prepared for, and make an escape soon as they hear the helicopter."

Investigators believe there are many more marijuana crops still undiscovered. California is estimated to be the largest marijuana producer among some 15 producing states.

"We're not getting all of them," Brown said. "The reality is that we are seeing an increase in the numbers. That's cause for concern."

Although the wildfire appeared to be an accident, illicit marijuana production carries its own dangers. Authorities say growers sometimes set traps or use armed guards.

In Santa Barbara County, at least one slaying has been linked to pot production. Authorities accused four men of killing Adan Cervantes Ruiz, 23, who was shot and left wrapped in a sleeping bag along a highway near Los Olivos in September 2007. However, charges were dropped earlier this year because of insufficient evidence.

Authorities contend he was killed by men transporting packaged, processed marijuana from a farm south of Lompoc. A week later, authorities raided the fields, recovering about 93,000 plants. Five people were arrested, including Ruiz's brother.