DANNEMORA, N.Y. — Two convicted killers used power tools to cut through steel pipes at a maximum-security prison near the Canadian border and escape through a manhole, Gov. Andrew 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 Dannemora, N.Y.

He said Richard Matt, 48, and David Sweat, 34, “are two dangerous individuals.”

Sweat is serving life without parole for killing a Broome County sheriff’s deputy in 2002. Matt is serving 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 Annuci, the 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.”

State police say the search for the prisoners includes more than 200 officers, bloodhounds and aerial surveillance.