(AP) -- Police expanded the search Wednesday for two escaped murderers beyond a 16-square-mile (40-square-kilometer) area of woods, fields and swamps where the manhunt has been most intense, even as rainy weather hampers their progress.

The more than 800 law enforcement officers combing the rural area now have shifted their focus eastward leading from the village of Dannemora, home of the Clinton Correctional Facility where the prisoners served time, in far northern New York state.

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

No vehicles were reported stolen in the area, which led searchers to believe Matt and Sweat were still near the prison. Search dogs caught the scent of the men, and authorities found evidence indicating they may have spent time there.

But police say that rain has been washing away any scent dogs might find and interfering with thermal imaging devices being used to detect body heat.

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.

A prison worker has been charged with helping the killers flee by providing them with hacksaw blades, chisels and other tools.

Prosecutors say Joyce Mitchell, a prison tailoring shop instructor who befriended the inmates, had agreed to be the getaway driver but backed out because she still loved her husband and felt guilty for participating.

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

But local police chief David 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."

Mitchell was charged Friday with supplying contraband, including a punch and a screwdriver, to the two inmates. She has pleaded not guilty. She has been suspended without pay from her job overseeing inmates who sew clothes and learn to repair sewing machines.

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. Prosecutors say they apparently used tools stored by prison contractors, taking care to return them to their toolboxes after each night's work.

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Associated Press writer Michael Virtanen in Albany contributed to this report.