DANNEMORA, N.Y.  — Police blocked off the main road outside a northern New York village as authorities on Thursday concentrated their sixth day of searching for two escaped murderers on a swampy area just a couple of miles from the prison the convicts broke out of last weekend.

State police closed Route 374 on Thursday morning as well as other nearby roads just east of Dannemora, where David Sweat, 34, and Richard Matt, 48, used power tools to cut their way out of maximum-security Clinton Correctional Facility.

A police helicopter flew over a heavily wooded area dotted with swamps as troopers and corrections officers stood guard at regular intervals along a mileslong stretch of a nearby road. The search area appeared to be focused about 2 miles east of the prison, where the escape was discovered early Saturday by guards checking the inmates’ neighboring cells.

Local schools were closed Thursday, and residents were told by authorities to lock their doors.

The renewed activity so close to the prison appeared to be the best hope of catching the two convicts since Wednesday, when authorities acknowledged being in the dark about their whereabouts or doings, even as the hunt for the men expanded past state borders.

At a news conference outside the prison Wednesday, New York State Police Superintendent Joseph D’Amico said, “I have no information on where they are or what they’re doing, to be honest with you.”

Authorities expanded the search after investigators learned that the inmates had talked before last weekend’s breakout about going to neighboring Vermont.

“We have information that suggests they thought New York was going to be hot. Vermont would be cooler, in terms of law enforcement,” Vermont Gov. Peter Shumlin said at the news conference with New York Gov. Andrew Cuomo.

Shumlin and other officials would not say how authorities learned that information.

On Thursday morning, a Philadelphia cab driver reported picking up two men who matched the descriptions of the escaped killers and dropping them off at the city’s Amtrak station. Police Commissioner Charles Ramsey said such possible sightings have been reported in several cities and he had no reason to think the inmates were in Philadelphia.

Meanwhile, another search began Wednesday night closer to the prison.

D’Amico said a prison employee — identified in news reports as Joyce Mitchell, a training supervisor at the prison tailor shop — had befriended the killers and “may have had some role in assisting them.”

He would not elaborate.

Mitchell’s son, Tobey Mitchell, told NBC that she checked herself into a hospital with chest pains Saturday. He said she wouldn’t have helped the inmates escape.

Using power tools, Sweat and Matt cut through a steel wall, broke through bricks and crawled through a steam pipe before emerging through a manhole in the street outside the 3,000-inmate Clinton Correctional Facility in far northern New York, about 20 miles from the Canadian border.

The inmates may have had a head start of several hours before guards noticed they were missing, Cuomo said.

Authorities suspect the inmates had help from the inside in obtaining the power tools. Unions representing guards and civilian staff members at the prison said many have been questioned by investigators, but no one has been disciplined or charged.

Vermont authorities are patrolling Lake Champlain and areas alongside it, Shumlin said. Cuomo urged the people of Vermont to be on the alert and report anything suspicious, warning: “Trust me, these men are nothing to be trifled with.”

A road east of Dannemora remained closed Thursday morning at state troopers manned road blocks, and the 1,500-student Saranac Central School District called off classes because of all the police activity in the area 4 miles east of the prison.

As part of the search, state troopers and correction officers in helmets and body armor retraced their steps around the prison, checking garage doors, sheds, windows and other structures for signs of a break-in or other clues.

More than 450 federal and state law enforcement officers were taking part in the search, including customs agents, federal marshals and park rangers.

The killers’ mugshots have been put on more than 50 digital billboards in New York, New Jersey, Massachusetts and Pennsylvania, police said, and a $100,000 reward has been posted.

Law enforcement officials again asked the public to report anything out of the ordinary.

“We don’t want them out searching the woods,” Sheriff David Favro said. “But if you’re sitting on your porch, get your binoculars out and see if you see something unusual.”

In Dannemora, Barbara McCasland said officers asked to search her home, but she told them no.

“I’m pretty battened down here,” she said. “My windows are locked and everything.”

As the manhunt dragged on, she said she was getting worried: “I wasn’t in the beginning, but seeing that they’ve been out there so long, I am a little nervous.”

Many in the prison town greeted the return of the searchers with a shrug. Many suspect Sweat and Matt are long gone and they are past any danger.

“I’m not worried about it,” Jackie Trombley said.

Referring to the searchers swarming the area, she said: “We’ve got these guys down the road. They’re everywhere, so it really doesn’t bother me.”

Virtanen reported from Albany.