Escaped New York convicts added to 'most-wanted' list

US Marshals have added the two killer convicts who escaped a maximum-security prison two weeks ago to a 15 most-wanted list of "the worst of the worst" fugitives.

Richard Matt, 49, and David Sweat, 35, escaped 13 days ago from New York's Clinton Correctional Facility in an elaborate prison break that has been likened to a Hollywood movie.

Joyce Mitchell, who worked in the tailor shop at the prison in the village of Dannemora is in custody charged with facilitating their escape, which saw them use hacksaw blades to bust out of their cells before crawling along pipes and out into freedom via a manhole cover.

Police say they have 1,400 leads in the hunt for the duo, described as dangerous and not to be approached in any circumstances.

"The agency’s 15 Most Wanted fugitive list is reserved for the worst of the worst," said US Marshals Service Director Stacia Hylton.

"There is no question David Sweat and Richard Matt fall into this category.

"While their brazen prison escape has left the public on edge, it has only ignited our sheer determination to bring them back to justice."

New York State Police Superintendent Joseph D'Amico said putting the on-run pair on the notorious list was a way of garnering public attention and generating new leads.

"We are absolute in our commitment to apprehend these dangerous escapees and will leave no stone unturned," added Northern District of New York US Marshal David McNulty.

"Sweat and Matt have violent criminal histories and pose a significant threat to anyone who may come in contact with them."

Matt, six feet (1.83 meters) tall with multiple tattoos, was serving a sentence of 25 years to life for the 1997 kidnapping and dismembering of his former boss.

He fled to Mexico after the murder and killed another American there, before being sentenced to 20 years and extradited back to New York.

Sweat was serving a life sentence without parole for murdering a sheriff's deputy in New York state in 2002 when he was 22.

The Marshals Service is offering a reward of up to $25,000 for information leading directly to the apprehension of either man.