DANNEMORA, NY — (CNN) Law enforcement converged on a site Thursday in upstate New York where bloodhounds picked up the scent of what authorities suspect came from escaped convicted murderers Richard Matt and David Sweat, sources said.

A large-perimeter search area has been set up around the site, about 3 miles from the Clinton Correctional Facility in Dannemora, according to a state official and another source briefed on the investigation. Guards found out about the killers’ escape from the maximum-security prison during a bed check early Saturday.

In addition to the scent, investigators found an imprint either from a shoe or boot as well as food wrappers in the area, one of the two sources said. Clinton County District Attorney Andrew Wylie said that possible bedding — an indent in the grass or leaves — has also been discovered.

“If they are not good in the woods, it’s an instant trap when they get out,” former FBI agent and onetime Navy SEAL Jonathan Gilliam told CNN. “… If you have to steal food or steal a car, that’s going to leave more clues.”

Thomas LaSalle, who stays locked in his house as authorities do their work, describes the area as rugged terrain with fallen trees, moss-covered boulders and thick forest everywhere. As a Scout growing up, he knew never to tackle this country for more than a day or two at a time.

“The mosquitoes, the black flies and the ticks, it’s got to wear you down,” LaSalle said. “It’s rough stuff. … I can’t imagine that they’ve gotten much left in them.”

The jailbreak has transformed the rural, idyllic swath of northeast New York from a place where people go to get away from the crowds and crime of urban life into something closer to a “military state,” as one resident described it.

“Life has been insane,” Steve Lashway, who runs a meat market and deli in Dannemora, told CNN on Thursday. “We have … officers on every corner with shotguns, and there are roadblocks up everywhere.”

Authorities closed down parts of New York State Route 374 on Thursday “until further notice” because of a lead from the previous night, New York State Police spokesman William Duffy said. Checkpoints were set up along a stretch from Dannemora east to West Plattsburgh, while authorities looked for clues.

Searches were underway in hundreds of seasonal homes in a 5-square-mile area in and around West Plattsburgh, with helicopters equipped with thermal cameras providing support, officials said.

The law enforcement presence and possibility of killers on the loose prompted the cancellation of classes Thursday in the Saranac Central School District, which includes Dannemora. LaSalle called the ordeal “very unnerving,” with police everywhere he can see and helicopters overhead.

“I got the shakes, it’s a lot of excitement,” he said. “It’s like a lockdown.”

The area isn’t the only place law enforcement is looking.

Vermont state police vessels and troopers have searched on Lake Champlain, which straddles the two states, as well as in nearby campsites.

But Vermont Gov. Peter Shumlin acknowledges that “we really have no idea where they are.”

“This is a governor’s nightmare,” he added. “We’re trying to protect the public safety and take care of our folks (because) these guys are dangerous, they are desperate, and they would do anything to continue their freedom.”

Hundreds of officers have scoured the woods, looking “behind every tree, under every rock and inside every structure” for Matt, 48, and Sweat, 34, New York State Police Superintendent Joseph D’Amico said.

Earlier this week, they searched farms, fields and woods in Willsboro after a driver saw two “suspicious” men run off during a late-night rainstorm.

Authorities can’t discount the possibility that Matt and Sweat have left the area, perhaps heading to Canada — 20 miles north of the prison. Fifty digital billboards with the fugitives’ photos have gone up in New York, New Jersey, Massachusetts and Pennsylvania.

“(Authorities) are not just staying local,” Lenny DePaul, a former regional task force commander for the U.S. Marshals Service, told CNN on Thursday. “(People should) not think that they’re cornered somewhere in New York. So they have to keep their eyes open and be vigilant.”

Lashway, the Dannemora market owner, said, “It’s been crazy with all the rumors.

“Just about every day, somebody comes into the shop and says, ‘They’ve got ’em. They’ve got ’em.’ But nope, they don’t.”

Authorities have been looking for Matt and Sweat since Saturday morning.

The two used power tools to get out of their cells and cut into a steam pipe, navigating a tunnel of pipes and finally surfacing out a manhole.

Sweat was serving a life sentence without parole for fatally shooting and then running over Broome County Sheriff’s Deputy Kevin Tarsia.

Matt held a businessman hostage for 27 hours, and then tortured and killed him after he wouldn’t give him more money.

State data show that most escapees in New York are captured within 24 hours. Of 29 inmates who fled between 2002 and 2013, only one was free for more than two days.

How have they done it?

With help, many say they believe.

D’Amico said Joyce Mitchell, an industrial training supervisor at the prison who worked with the convicts in a tailoring shop, had befriended the men and “may have had some sort of role in assisting them.”

The state police superintendent did not elaborate. But according to a source close to the investigation, authorities believe Mitchell planned to pick up the inmates after their escape but changed her mind at the last minute. Her cell phone was used to call people connected to Matt, according to another source. It’s unclear who made the calls, when they were made or whether Mitchell knew about them.

Mitchell told investigators that Matt made her feel “special,” though she didn’t mention being in love with him, a source familiar with the investigation said.

While she didn’t warn authorities about the escape, she has answered all their questions each time they’ve gone back to her, a New York state official said.

Authorities are holding off on any move to charge her with being an accomplice, hoping instead to have her continued cooperation, a New York state official told CNN. Wylie, the Clinton County district attorney, declined to comment.

Mitchell’s family is standing behind her, with her daughter-in-law telling CNN that “95% of what is being said” is not true.

Paige Mitchell denied that her mother-in-law was to be the getaway driver and that she helped provide the power tools used in the escape. She added that Matt may have persuaded her mother-in-law to contact people for him who knew about art, saying, “Her heart was in the right place.”

“They don’t have the facts to prove this,” she said. “This is just slander and rumor.”

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