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.