Serial killer Levi Bellfield has for the first time admitted abducting, raping and murdering schoolgirl Milly Dowler, police say.
Bellfield, who now calls himself Yusuf Rahim, made the admission during an investigation into whether he had an accomplice, according to the Surrey force.
Police said they had arrested a man in his 40s on Wednesday in relation to allegations of rape and assisting an offender, but not murder.
Officers later released him without charge over the claims, after finding no evidence to support them.
Bellfield was given a whole-life prison sentence in June 2011 for killing 13-year-old Milly nearly 14 years ago.
A Dowler family statement said: "The Dowler family has been made aware of the recent arrest.
"They have been aware for some considerable time that a new police investigation was taking place into the circumstances of the abduction and murder of Milly.
"The effect of this information has been devastating for a family which has already had to endure so much.
"We must stress how important it is that, notwithstanding this development, the Dowler family should be afforded privacy and space to go about their lives."
When Bellfield went on trial, he was already in jail for the murders of Amelie Delagrange and Marsha McDonnell, and the attempted murder of Kate Sheedy.
Milly was making her way from school to her home in Walton-on-Thames, Surrey, when she was snatched in March 2002.
Her body was found in a wood in Yateley Heath, Hampshire - 25 miles from Walton-on-Thames. Experts could not say how she died.
Bellfield lived 50 metres from where she went missing but he did not become a suspect until he was arrested by police in London for the other crimes in 2004.
In February 2012 he lost a bid to challenge his conviction at the Court of Appeal in London.
A spokesman for Surrey Police said on Wednesday: "During this investigation police have also spoken to Levi Bellfield and he has admitted his responsibility for the abduction, rape and murder of Milly Dowler.
"Despite his conviction, this is the first time Bellfield has made such admissions to police."