New York state police are planning to expand the search area for two escaped murderers beyond a 16-square-mile area of wooded terrain and swamps, officials said Tuesday.

Clinton County Sheriff David Favro said the rainy weather has been washing away any scent dogs might find, as well as interfering with thermal imaging devices used to detect body heat.

Searchers still believe that convicts David Sweat and Richard Matt are near the prison because there have not been reports of any stolen cars in the area. Search dogs have repeatedly caught the scent of the men and authorities found evidence indicating they may have spent time there.

The more than 800 law enforcement officers combing the rural area now have shifted their focus eastward along Route 374 leading from the prison town of Dannemora.

Matt and Sweat escaped June 6 from the maximum-security prison near the Canadian border.

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Sweat, 35, was serving a life sentence without parole in the killing of a sheriff’s deputy. Matt, 48, was doing 25 years to life for the kidnap, torture and hacksaw dismemberment of his former boss.

Meanwhile, Joyce Mitchell, a former prison worker, was charged with aiding the men in their escape by providing hacksaw blades, chisels and other tools. She was visited in jail Tuesday by her husband who is also a prison worker.

Favro described Mitchell as “composed” during the visit with her husband, Lyle Mitchell.

Prosecutors accuse Mitchell of planning to be the getaway driver for the two men once they escaped. However, they say she backed out because she still loved her husband and felt guilty for participating despite befriending the men.

District Attorney Andrew Wylie said Monday that there was no evidence the men had a Plan B once Mitchell backed out of the escape.

But Favro said that while he has "no concrete information," he doesn't believe the escapees would have counted only on Mitchell for the success of their "elaborate, well-thought-out escape plan."

"My theory — my theory only — is that she was Plan B," he said Tuesday. "I would have viewed her as baggage, almost, for them to be able to escape into freedom because she's leaving behind a family and a husband."

He said investigators won't be certain until the fugitives are caught.

But Favro said, "I find it difficult to believe right from Day 1 that they would go through that — probably took some time to really map together — and they would get out on the hopes that a civilian worker that they found would assist them in actually getting away."

Mitchell was charged Friday with supplying contraband to the inmates. She pleaded not guilty. Since then, she has been suspended without pay from her $57,000-per-year job as a tailor.

Authorities say the convicts used power tools to cut through the backs of their adjacent cells, broke through a brick wall and then cut into a steam pipe and slithered through it, finally emerging outside the prison walls through a manhole. Wylie says they apparently used tools stored by prison contractors, taking care to return them to their toolboxes after each night's work.

In Broome County, where Sweat and his cousin killed a deputy in 2002, Sheriff David Harder said his office has been investigating since Sweat broke out of prison, contacting his family and associates and committing about 50 officers to the case. Sweat was "a kind of survivalist," who was caught in the woods in New York's Southern Tier five days after that killing after someone came forward with information, he said.

The Associated Press contributed to this report.