Ian Brady's mental health advocate has told police she gave a letter in which he apparently reveals the location of one of his victims back to him, sources have said.
Police launched an investigation after Jackie Powell told a Channel 4 documentary the Moors murderer gave her a sealed envelope to pass to Winnie Johnson, mother of 12-year-old Keith Bennett, in the event of his death.
The TV production team passed on the information to Greater Manchester Police on July 30 and Ms Powell, 49, who was appointed Brady's mental health advocate in 1999, was detained on Thursday on suspicion of preventing the burial of a body without lawful exercise.
But police sources said Ms Powell claims she returned the envelope to Brady at some point between July 30 and her arrest.
Detectives examining a large number of documents seized from Ms Powell's home in South Wales have so far found no letter or any evidence to suggest Brady has disclosed the location of Keith's body. A search of Brady's cell at Ashworth Hospital in Merseyside has also failed to uncover the alleged letter. Ms Powell has been released on bail pending further inquiries.
Martin Bottomley, head of investigative review at Greater Manchester Police's major and cold case crime unit, said his officers were trying to establish if the letter exists or is "simply a ruse". He said: "I want to be explicitly clear about this: Ian Brady has not revealed to police the location of Keith's body. What we are looking at is the possibility, and at this stage it is only a possibility, that he has written a letter to Keith's mum, Winnie Johnson, which was not to be opened until after his death."
Brady, 74, has always refused to disclose the location of Keith's body. His refusal has caused constant heartache for Mrs Johnson, who has cancer, and recently appealed to him to break his silence before she died. She is receiving care in a hospice and is said to be unaware of the developments.
Her lawyer, John Ainley, a senior partner at Oldham-based North Halliwell Ainley, said he was "sceptical" about the possibility that Brady has revealed the location of Keith's body.
There was no sign of life at Ms Powell's semi-detached home in Llangennech, with neighbours saying she had gone to stay with friends.
One said: "She's been quite used to dealing with stressful situations via her work, but I imagine the events of the past few days have been quite demanding. She's a pleasant sort of lady and always says hello. I don't know what to say about her arrest, or the whole Ian Brady thing. No one round here knew that she even knew him or worked with him until we saw the news. But she's the kind of woman who would go out of her way to help people, so I'm sure she's been more than helpful to police and their inquiry."