DANNEMORA -- Two convicted murderers used power tools to cut through steel pipes at a maximum-security prison near the Canadian border and escape through a manhole, Gov. Andrew M. Cuomo said Saturday.

"It was an elaborate plot," Cuomo said after joining law enforcement authorities to retrace the prisoners' escape route from the Clinton Correctional Facility in upstate Dannemora.

He said Richard Matt, 48, and David Sweat, 34, "are two dangerous individuals." Sweat is serving a sentence of life without parole after he was convicted of first-degree murder for killing a Broome County sheriff's deputy in 2002. Matt is serving a sentence of 25 years to life for kidnapping a man and beating him to death in 1997.

The two men's adjoining cells were empty during a morning check, said Anthony Annucci, the acting state corrections commissioner.

"A search revealed that here was a hole cut out of the back of the cell through which these inmates escaped," Annucci said. "They went onto a catwalk which is about 6 stories high. We estimate they climbed down and had power tools and were able to get out to this facility through tunnels, cutting away at several spots." Authorities said there are many questions including how the men acquired the tools. Annucci said prison authorities were checking to see if any power tools were missing from contractors at the facility.

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Cuomo said the prison break was the first escape from the maximum-security portion of the facility since it was built in 1865.

Sweat is a 5-foot-11 with brown hair and green eyes, weighing 165 pounds, police said. He has tattoos on his left bicep and his right fingers.

Matt is 6-foot with black hair and hazel eyes, according to police. He weighs 210 pounds and has tattoos including "Mexico Forever" on his back, a heart on his chest and left shoulder and a Marine Corps insignia on his right shoulder.