13-yr-old Milly Dowler (left) was murdered in 2002. Levi Bellfield (right) was found guilty of abducting and killing Milly Dowler
Serial killer Levi Bellfield has admitted abducting, raping and killing 13-year-old Milly Dowler for the first time, according to Surrey Police.
Bellfield, 47, was given a whole-life prison sentence in June 2011 for murdering the schoolgirl.
He made the admission during an investigation into whether he had an accomplice, police said.
Milly's family described the news as "devastating for a family which has already had to endure so much".
Surrey Police revealed it had arrested a man in his 40s who has since been released without charge.
Detectives from the Surrey and Sussex Major Crime Team made the arrest following new information regarding an accomplice being involved in the abduction and rape, but not murder, of Milly Dowler.
They said no evidence had been found to support that claim.
In a statement issued through solicitors, Milly's family said they had been made aware of the recent arrest and Bellfield's admission.
"The effect of this information has been devastating for a family which has already had to endure so much," they said.
Milly was kidnapped while on her way from school to her home in Walton-on-Thames, Surrey, in March 2002.
Analysis: Tom Symonds, BBC Home Affairs Correspondent
Bellfield wasn't arrested and charged until detectives connected him with two other horrific murders - those of Marsha McDonnell and Amelie Delagrange and the attempted murder of a young woman called Kate Sheedy.
But this admission today makes little difference.
Despite admitting what he's done, he is serving what is called a whole life tariff - so he will never be released.
Her body was later found 25 miles away in Yateley Heath, Hampshire. Experts could not say how she died.
Bellfield was found guilty of abducting and murdering the teenager following a trial at the Old Bailey where a judge described him as a "cruel and pitiless killer".
He was already in jail for the murders of Amelie Delagrange, 22, and Marsha McDonnell, 19, and the attempted murder of Kate Sheedy, 18, when he went on trial accused of killing Milly.
Bellfield, who now calls himself Yusuf Rahim, lived 50 yards from where Milly vanished but did not become a suspect until he was arrested by police in London for the other crimes in 2004.