Two convicted murderers left a taunting note for guards after using power tools to dig their way out of a maximum security prison in upstate New York.

A huge manhunt is under way for Richard Matt, 48, and David Sweat, 34, who busted out of Clinton Correctional Facility sometime between Friday night and early Saturday.

Speaking to Jonathan Healy on today's Pat Kenny Show, Terry Sheridan - 24/7 News Reporter in New York City - explained how the prisoners escaped. He said that a female prison worker has been suspended and will now be questioned about the escape:

Police said the duo were found missing from their adjoining cells during a Saturday morning roll call.

They are thought to have burrowed more than a city block before emerging from a manhole on to a street.

The pair left sweatshirts and other clothing in their beds as decoys to make it appear as though they were still in their cells.

They also left a note with a caricature of a smiley face saying: "Have A Nice Day."

New York Governor Andrew Cuomo travelled to the facility on Saturday in Dannemora, about 20 miles (32km) from the Canadian border, to see for himself the route the men took to freedom.

He told reporters: "There's no doubt that it was an extraordinary act.

"I mean, you have a facility that opened in 1865. Just think about it, this is the first escape from the maximum security portion of the institution ever."

The escape has seen parallels drawn with 1994 prison break movie The Shawshank Redemption.

But Governor Cuomo warned the fugitives are cold-blooded killers who should not be approached by any member of the public.

"These are two dangerous individuals, one was incarcerated for killing a sheriff," he said.

"And they are nothing to be trifled with."

Mr Cuomo said he suspected that some of the other prisoners must have been aware of the men's digging.

"I chatted with a couple of the inmates myself and said, 'You must be a very heavy sleeper,'" the governor said.

"They were heard, they had to be heard."

After cutting through the steel back walls of their cells, they are thought to have accessed a twisting series of pipes and tunnels, which they also cut their way into.

Anthony Annuci, the acting state corrections commissioner, said: "They went on to a catwalk which is about six storeys 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."

Investigators were looking into how the men acquired the tools, and whether any were missing from contractors at the prison.

More than 200 law enforcement officers have been deployed in the manhunt, assisted by a variety of tactical support, including K-9 units, SWAT teams and helicopters.

Heavily armed police set up road blocks in an attempt to hunt down the two men.

Matt - who has a tattoo reading Mexico Forever - was serving 25 years to life for kidnapping a man and beating him to death.

Sweat was serving a life sentence without the possibility of parole for the murder of a sheriff's deputy.

About 3,000 inmates are incarcerated at the all-male prison.