Last Updated Jun 15, 2015 10:15 PM EDT
DANNEMORA, N.Y. -- The prison seamstress who authorities say helped two convicted killers escape from a maximum security prison in upstate New York had an intimate relationship with one of the prisoners, CBS News has learned.
A law enforcement source confirmed that Joyce Mitchell told authorities she was involved with prison inmate Richard Matt and gave details of their encounters.
CBS News learned earlier Monday that police believe the prison employee at the center of the escape smuggled tools to the escapees with the understanding that the convicts would kill her husband.
Law enforcement officials are investigating the alleged threat to determine if it was an attempt by Matt and fellow inmate David Sweat to force her to help them and keep her quiet about their escape plans, or if she had willingly plotted the murder of her husband with them.
Mitchell pleaded not guilty Monday. But the inmates remain the focus of an intense manhunt in upstate New York.
Mitchell, 51, is already facing a felony charge for allegedly helping the two murderers escape from prison. Now a law enforcement source tells CBS News there was an agreement between Mitchell and the two men, Matt and Sweat, that once out of prison they would kill her husband Lyle.
In an interview Sunday, Clinton County District Attorney, Andrew Wylie would not confirm there was any threat to Mitchell's husband. He says she told investigators the reason she didn't follow through with the plan was that she was worried about her husband.
"That was one of her final statements that she made to us, that she did love Lyle and that she didn't want to hurt him in that way," said Wylie.
Wylie revealed more details about the escape plan, saying Mitchell told investigators she was to pick up the two men at the power plant near the prison after they escaped.
"She was not advised where it was but it was about seven hours away and that they would need a 4-wheel drive vehicle to get into that area," he said. He says Mitchell had a panic attack and went to a hospital instead.
Area residents are taking no chances. Ken Snyder, a former corrections officer who worked at the prison, lives along the search perimeter. He told us he has dead-bolted part of his home and has his rifle ready.
Joyce Mitchell's new attorney told us she has not spoken to her husband and is distraught. When asked if Mitchell was on suicide watch, the sheriff told us, they don't use the term but she is on one-on-one supervision.