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Officers closely searched two areas at opposite ends of New York on Sunday for prison escapees David Sweat and Richard Matt, who could be hitching rides on trains, authorities said.

More than 300 law enforcement officers combed the southern town of Friendship after a woman reported seeing men who matched the descriptions of Matt and Sweat by railroad tracks near her home. By Sunday night, they were also searching in the upstate area of Owls Head and Mountain View, about 30 miles west of Clinton Correctional Facility, which they escaped from more than two weeks ago, state police told NBC News.

Police have received hundreds of tips since David Sweat and Richard Matt escaped Clinton Correctional Facility in Dannemora on June 6, but one called in Saturday from Friendship — nearly 400 miles from the prison — caught their attention.

State Police Maj. Michael Cerretto said a woman called police a bit after 1 p.m. ET Saturday and said she had spotted two men who looked like Matt and Sweat in Friendship, which is just north of Pennsylvania.

"We determined that she was credible and that this should be investigated," Cerretto said during a news conference Sunday.

The woman, Brandy Thompson, told NBC station WGRZ of Buffalo that she saw the men by the railroad tracks about a football field away. When her dog barked, they ran off, she said.

Thompson called 911, and police were at her home within about eight minutes. She said she was keeping her .30-06 rifle by her side "until I hear 'all clear.'"

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Cerretto said that aviation, canine and special operations teams were deployed to Friendship and that police were asking residents to "be on alert."

But NBC News observed officers leaving the area throughout Sunday afternoon, by the evening, the focus of the search appeared to have shifted upstate, to Franklin County.

A large police presence converged on the area between Owls Head and Mountain View, not far from the Vermont border. State police officials confirmed to NBC News that they were searching there in a remote area that is dotted with numerous camps and cabins.

Possible sightings of Matt and Sweat in such far-flung parts of the state suggested that the fugitives weren't traveling solely on foot, said Sen. Charles Schumer, D-New York.

"If the prisoners were actually in Allegany County and Friendship," Schumer said Sunday.

"One possibility — not a certainty, but a possiblity — is they're riding the rails. And there’s a long train line that connects across southern New York that they might have ridden."

A week ago, witnesses reported seeing two men in a rail yard in Erwin, about 70 miles east of Friendship, according to state police. Two men were spotted heading toward the Pennsylvania border the next day, police said.

On Friday, a Clinton correctional officer, Gene Palmer, was placed on leave "as part of the ongoing investigation" into the escape, according to police. A senior official said Palmer is being investigated for what role or knowledge he may have had of the escape plot.

Palmer's lawyer, Andrew Brockway, told NBC station WPTZ of Plattsburgh, New York, that his client was "completely forthcoming" during 14 hours of questioning Saturday.

Brockway said Palmer has worked at the maximum-security penitentiary for 28 years. He was assigned only to the "honor block," which meant he had extensive, daily contact with Matt and Sweat.

But "I can 100 percent confirm that he did not know they were planning on breaking out of the prison," Brockway said.

Police executed a search warrant Friday night at Palmer's home. Brockway would not confirm that they were looking for a painting Matt gave Palmer at some point in the past.

"Several" prison employees are being probed for what they knew about the escape plot, according to a source, but only one person, prison worker Joyce Mitchell, has been arrested in alleged connection with their escape.