NEW YORK (Reuters) - Hundreds of law enforcement agents hunting for two upstate New York prison escapees focused their search on Thursday on a heavily wooded area just a few miles from the maximum security facility where they broke out last week, police said.

Convicted murderers Richard Matt, 48, and David Sweat, 34, escaped from the maximum-security Clinton Correctional Facility in Dannemora, New York through underground pipes and a manhole. They were discovered missing early on Saturday.

More than 500 law enforcement officers, along with sniffer dogs and aviation units, were involved in the manhunt, along with the FBI and other agencies, New York State Police said.

A stretch of highway in Dannemora just miles from the prison was off-limits to traffic and schools in the Saranac Central School District were closed due to the search, officials said.

A female prison worker questioned by police thought she had a romantic relationship with one of them and planned to drive the getaway car, NBC News reported.

However, Joyce Mitchell, an industrial training supervisor in the tailor shop got cold feet and checked into a hospital for nerves on Saturday, the day the inmates were discovered missing, NBC reported, citing unnamed senior government officials.

The older inmate, Matt, who has a history of escape attempts, wooed Mitchell for months and established a relationship in which she agreed to drive the getaway car, the report said.

The local Albany Times Union newspaper reported that Mitchell admitted to investigators to smuggling power tools and providing cell phone access to the inmates, citing anonymous law enforcement officials.

The ground search was focused on a heavily wooded area east of Dannemora, along New York State Route 374, following up on a lead, New York State Police said in a statement.

CNN, citing unidentified sources, reported that bloodhounds picked up the scent of the escapees about 3 miles from the prison.

Mitchell's statements to police were incriminating enough to result in her being indicted for her role in the escape, The New York Times reported.

Mitchell, who is married to another prison worker, earns a salary of $57,700 for the state corrections department job she has held since 2008, the Buffalo News reported.

Police have declined to comment further on Mitchell, but State Police Superintendent Joseph D'Amico said at a news conference on Wednesday: "She befriended the inmates and may have had some sort of role in assisting them."

(Reporting by Barbara Goldberg and Ellen Wulfhorst; Additional reporting by Curtis Skinner; Editing by Bernadette Baum and Cynthia Osterman)