DANNEMORA, New York — Two convicted murderers escaped from a maximum security prison in upstate New York by cutting through a steel wall and following a series of tunnels until they emerged from a manhole outside the prison walls, authorities said Saturday afternoon.

Richard Matt, 48, and David Sweat, 34, were discovered missing at the 5:30 a.m. “standing count” of inmates at the Clinton Correctional Facility in Dannemora, New York State Police said on the agency’s Facebook page.

An intense manhunt was underway with more than 200 law enforcement officers looking for the men — the first to escape from the maximum security portion of the prison, Gov. Andrew Cuomo said at a press conference.

“These are dangerous people,” he said. “They are nothing to be trifled with.”

The prisoners apparently were last seen at 10:30 p.m. Friday during a standing count, authorities said.

Head counts are performed every two hours throughout the night when guards visually check to see whether inmates are in their bunks, Clinton Correctional Facility Supervisor Steven Racette said.

Matt and Sweat tricked the guards by arranging things in the bunks to look “like people were sleeping … with these sweatshirt hoodies on,” the governor said. The inmates were discovered missing at the 5:30 a.m. inmate count.

The men had side-by-side cells and apparently had obtained power tools to cut through the steel wall in their cells, authorities said.

The escapees followed a catwalk “down an elaborate maze of pipes into tunnels and exited a series of tunnels at the manhole cover,” Cuomo said.

Prison officials took Cuomo through the escape route.

“It was elaborate, it was sophisticated,” he said. “It involved drilling through steel walls, steel pipes.”

Authorities don’t know how the prisoners got the power tools. Clinton Correctional Facility was built in 1845 and undergoes regular maintenance, so it’s possible the tools came from the contractors and workmen who are often inside the facility, Cuomo said.

Sweat was serving life without parole after being convicted first-degree murder in the death of a Broome County sheriff’s deputy on July 4, 2002, state police said.

Matt is serving 25 years to life. He was convicted on three counts of murder, three counts of kidnapping and two counts of robbery after he kidnapped a man and beat him to death in December 1997, the state police said.

The prison in the northeast corner of New York is the state’s largest prison with a population of 2,689 inmates, the corrections department said.

CNN affiliate WPTZ reported that state police have set up roadblocks in the Dannemora area and that armed troopers are searching vehicles. Troopers and corrections officers are searching the woods in the area, too.