Heavily armed law enforcement officers in tactical gear converged Thursday on a small town in upstate New York miles from the maximum-security prison from which two convicted killers escaped in a "Shawshank Redemption"-style breakout over the weekend after a bloodhound picked up the scent of one or both of the murderers, a senior source familiar with the investigation told NBC News.
The dog picked up the scent late Wednesday, the source said, prompting authorities to close NYS Route 374 east of Dannemora as they set up a perimeter in hopes of ensnaring Richard Matt and David Sweat, who have now been on the run six days since their escape from Clinton Correctional Facility. The area remained closed Thursday as more than 500 personnel joined the hunt.
The potential development in the case comes as sources allege the prison tailor shop instructor questioned in the escape "thought it was love" with one of the men and had planned to be the duo's getaway driver before she got "cold feet" and checked herself into a hospital for a case of "nerves."
Those sources say Joyce Mitchell, a civilian employee who taught employees how to make Metro-North uniforms at the prison, was supposed to pick up the men after Saturday's escape, but she checked herself into an area hospital the day of the breakout, forcing the men to flee on foot.
A corrections department employee told NBC News inmates at the prison looked for the "weakest links" among the staff in an effort to exploit them for preferential treatment and that the "grooming" has become more of an issue than prison workers would like to admit. A former Clinton guard said any employee who showed compassion could become a target of the manipulation, mostly done to gain extra recreation time, newspapers and food.
Mitchell is expected to be charged in the breakout, sources familiar with the investigation tell NBC News, but she has not been arrested at this time.
Matt -- who was convicted of kidnapping, torturing and dismembering a former boss in 1997 -- had wooed her over the course of several months until she agreed to help the pair bust out of the prison 20 miles south of the Canadian border, the sources told NBC News.
"She thought it was love," the sources said.
Meanwhile, the multiagency, multinational dragnet for Matt and Sweat wears on. On Thursday, more than 450 officers scoured several states, while investigators in Philadelphia -- more than 400 miles south of the prison -- questioned a cab driver who said he thought he may have dropped the pair off at a train station. Investigators determined the cab driver's tip was unfounded.
New York State Police vowed Wednesday to look "behind every tree, under every rock and in every structure" until they find the men, and said they were "all-in" on the search amid a growing dragnet that saw police plead for help as far as Massachusetts, Vermont and Pennsylvania.
Gov. Cuomo and Vermont Gov. Peter Shumlin stood with state troopers to reassure the public and outline new tactical approaches based on information that Matt and Sweat may have talked about fleeing to Vermont. New York State Police were prepared to line the border in the effort to find the two men, who cut through a steel wall, broke through bricks and crawled through a steam pipe before emerging through a manhole outside the prison.
Sweat, 34, and Matt, 48, were discovered missing early Saturday after stuffing their beds with clothes to fool guards on their rounds and leaving behind a taunting note: "Have a nice day."
Cuomo said Wednesday the prisoners may have broken out as early as midnight, and state troopers said they were aware it was possible the murderers had a six-hour lead on police. Authorities said, though, that Matt and Sweat may not have taken advantage of that head start, and that's why they were continuing to search in areas near the prison as well as in other states and countries.
But at the late-afternoon news conference, D'Amico confessed, "I have no information on where they are or what they're doing, to be honest with you."
Fifty digital billboards were unveiled across four states -- from Massachusetts to Erie, Pennsylvania --on Wednesday, showing the killers' photos and urging the public to be on the lookout for them. Police in tactical gear with assault rifles were going door-to-door and set up a highway checkpoint in northern New York as law enforcement retraced the initial steps they made after the escape.
Law enforcement officials reiterated their plea for the public's help in reporting anything unusual in the area since the prison break. A $100,000 reward has been posted for information leading to the men' capture.
Sweat was convicted in the 2002 killing of a sheriff's deputy and was doing life without parole.
Matt was serving 25 years to life for the 1997 murder and had also been convicted of killing a man in Mexico while on the lam following his boss's death. He had previously escaped from prison, in 1986, and was deemed so dangerous that during a trial for the 1997 slaying, snipers were stationed atop roofs around the courthouse.