Swarms of state, local and federal agents combed thick woods east of the Clinton Correctional Facility, which Richard Matt, 49, and David Sweat, 35, busted out of, using power tools to cut their way out, before crawling along pipes and out to freedom via a manhole.
Investigators have focused on who helped Matt, who was convicted of dismembering his 76-year-old former boss, and Sweat, who shot dead a sheriff's deputy.
Mitchell was presented with the charges in court late Friday during an arraignment in which she appeared handcuffed and visibly nervous.
CNN and other US media reported that she plead not guilty.
More From This Section
Mitchell "provided some form of equipment or tools" that allowed the two murderers to escape, the Clinton County district attorney Andrew Wylie earlier told CNN.
Mitchell's arrest was "one large piece of the puzzle" in the hunt for the duo, Major Charles Guess of New York State Police told a press conference, adding: "We have a message for David Sweat and Richard Matt. We're coming for you and we will not stop until you are caught."
He had not been charged and was not in custody, Guess said, adding that wet weather and the rolling woodlands and hills where the search is focused were complicating the hunt.
But that might also slow the killer pair's progress, too, he cautioned.
"If they have not escaped the area or they have not availed themselves of shelter, we've got to assume they're cold, wet, tired, and hungry," he said.