Shawshank escapees
Law enforcement officers look out over a field near Willsboro, New York, last week after killers David Sweat and Richard Matt bust out of a New York prison. REUTERS/Chris Wattie

The female prison worker facing charges in court today for allegedly helping two killers escape from a New York prison had been previously investigated for a sexual incident with least one of them.

Following her arrest, she had told authorities she discussed a plan with both men to kill her husband, according to sources.

Prison authorities launched an investigation after a complaint that Clinton Correctional Facility tailor shop supervisor Joyce Mitchell, 51, was having a relationship with killer David Sweat, 35, District Attorney Andrew Wylie told NBC News. The other killer, Richard Matt, 48, may also have been a sexual partner, according to sources.There wasn't "sufficient information" at the time to remove Mitchell from the upstate prison or charge her, said Wylie.

Mitchell told investigators that she discussed a plan with both men that after she helped them escape they would kill her husband, a law enforcement source told the Albany-Times Union. Mitchell's husband, Lyle, is a maintenance worker at the same prison.

Mitchell brought in hacksaw blades, chisels, a drill bits and punch that helped the prisoners escape, according to the charges against her. She was also supposed to meet up with the escaped men and drive them seven hours to a hideout, but she backed out at the last minute, according to investigators. "She did indicate one of the reasons why she didn't show up was because she did love her husband and she didn't want to do this to him," said Wylie. She instead ended up at a hospital to be treated for a panic attack.

Mitchell, shackled, appeared briefly in court on Monday as her case was transferred to Clinton County Court. She has pleaded not guilty to promoting prison contraband in the first degree, a felony, and criminal facilitation in the fourth degree, a misdemeanor. More charges may be pending, according to Wylie.

Both escaped convicts, considered extremely dangerous, remain on the loose ten days after their escape.

More about Shawshank jailbreak