A female prison worker has been questioned over the brazen escape of two killers who used power tools to cut their way out of a maximum-security jail in New York state.

New York State Police confirmed the woman was being questioned as a possible accomplice, while Governor Andrew Cuomo said investigators were focusing on civilian employees at the Clinton Correctional Facility in Dannemora - rather than guards.

He told CNN: "We're looking at the civilian employees now and the private contractors to see if possibly a civil employee or contractor was assisting the escape because they wouldn't have equipment on their own, that's for sure."

"I'd be shocked if a correction guard was involved in this, but they definitely had help. Otherwise, they couldn't have done this on their own."

The woman is reported to have worked with David Sweat and Richard Matt tailoring clothing at the prison.

David Sweat (34) and Richard Matt (48) sliced through a steel wall, crawled down a catwalk, broke through a brick wall, cut their way into and out of a steam pipe and then sliced through a chain and lock on a manhole cover while making their escape sometime on Friday night.

They had stuffed their beds with clothes to fool guards and left behind a taunting note which read: "Have a nice day."

They are believed to have travelled the equivalent of a city block during the escape, before emerging on to a street.

Witnesses said to have seen convicts

A US$100,000 reward has been offered for information leading to the men's capture.

Officials have said an inventory has so far showed none of the prison's power tools was missing, but contractors typically come into the facility with equipment.

Roadblocks have remained in place around the prison, which is 20 miles from the Canadian border.

Two men claimed to have spotted the two convicted murderers shortly after they escaped from the jail.

One of the witnesses told ABC News he saw Matt and Sweat in his backyard, carrying what appeared to be a guitar case.

He said that when he confronted them, one of the escapees said: "We're just lost. We don't know where we are. We're on the wrong street."

They then ran off, he added.

The escape, which has drawn comparisons to the 1994 prison break film 'The Shawshank Redemption', was the first ever at Clinton Correctional Facility, which opened in 1845.

Matt, who has a tattoo which says Mexico Forever, was serving 25 years to life for kidnapping and dismembering his former boss in 1997.

Sweat was serving a life sentence without the possibility of parole for the murder of a sheriff's deputy in 2002.

Mr Cuomo said the fugitives may have crossed into Canada, or headed to another state or Mexico, where Matt served time for killing a man in 1998.