Richard Matt, 49, and David Sweat, 35, used power tools to cut their way out of their cells at the Clinton Correctional Facility before dawn on June 6 in a spectacular prison break likened to a Hollywood movie.
The audacious escape sparked a huge search involving more than 1,100 personnel backed by sniffer dogs and helicopters to find the men, who have reportedly been spotted in several locations in recent days in upstate New York.
"We have developed evidence in our search area that the suspects may be headed towards Canada," Major Charles Guess of New York State Police told reporters.
"We cannot get into specifics of the evidence we have recovered while investigating this particular lead. That evidence is still being evaluated by our laboratory as part of the investigative process.
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"But based on what we know at this point, we have a high degree of confidence in our conclusion.
Two prison workers have been charged over the brazen breakout, and Matt and Sweat -- whom police described as dangerous and probably armed -- have left tantalizing scraps of evidence as to their whereabouts including DNA evidence.