MISSOULA - A Montana fugitive and ex-militia leader has been on the run since a Sunday shootout with deputies, but the trail has gone cold.

Missoula County Sheriff Carl Ibsen said Thursday that deputies were trying to develop leads to find David Burgert, who authorities say ran off into the Lolo National Forest after exchanging shots with deputies following a low-speed car chase.

Police think Burgert is hiding somewhere in the mountains near the Montana-Idaho border, an area of towering peaks, low brush and thick pine forests. In recent decades, this remote region has proven fertile ground for extremist groups including the Militia of Montana, the neo-Nazi Aryan Nations and many others.

Burgert once led an anti-government militia in northwestern Montana known as Project 7. It was broken up after Burgert was arrested in 2002 on weapons charges. He spent eight years in federal prison before being released in March 2010.

A search effort that began with dozens of armed federal and local agents combing the forest focused Thursday on road patrols and pursuing leads developed from search warrants. Those warrants were sealed at the Missoula County courthouse.

Deputies have received numerous tips, but none have panned out. The Missoulian reported one concerned a man walking alone in the woods with a satellite phone; another, a man who resembled Burgert and was trying to enter Canada without a passport. The U.S. Border Patrol determined it wasn't the fugitive.

"Somebody called saying they saw some guy in a 7-Eleven in Wisconsin who looked like Burgert," said Undersheriff Mike Dominick. "Tips like that aren't going to do me any good here in Montana."

Burgert may have used a stashed tan Jeep Cherokee to escape. Deputies also reported hearing a gunshot shortly after Burgert fled into the woods on Sunday, but Ibsen said there was no indication he may have shot himself. There are no plans to bring cadaver dogs into the area, Ibsen said.

"If this takes a day, a week, a month or 40 years, we will never stop," Dominick said. "If you try to kill a Missoula County deputy, Missoula County will never stop."

After his release from prison, Burgert lived for a time at an apartment in Missoula. A man who answered the telephone at the apartment management company Thursday said Burgert did not cause any problems as a tenant. The man declined to give his name or answer additional questions.

More recently, Burgert had reportedly been living in his vehicle at picnic sites and campgrounds along Highway 12 near the town of Lolo. That's where deputies went Sunday to check on a vehicle that was reported parked for some time at the Fort Fizzle day-use area. Burgert took off, and the chase ensued.

Officers have recovered two Jeeps registered to Burgert. Both contained ammunition.

At the time of Burgert's 2002 arrest, U.S. authorities said Project 7 planned to kill officials in a plot to overthrow the federal government. Burgert was caught with a military-style assault rifle, and deputies recovered thousands of rounds of ammunition.

A former Marine who has been diagnosed with paranoid personality disorder, Burgert was convicted in 2003 of illegally possessing a machine gun.

Since his release from prison, there is no indication he has contacted his former militia associates, associates say.

The Associated Press tried to reach several of those associates in Montana by telephone. No one answered other calls to the home of Burgert's ex-wife.