Serial killer Levi Bellfield's shock confession to the murder of Milly Dowler has prompted police to review probes into "a number" of other crimes.
Bellfield, who was given a whole-life prison sentence in June 2011 for killing the 13 year old, made the admission for the first time during an investigation into whether he had an accomplice, Surrey Police said.
The Metropolitan Police confirmed it was looking at new information relating to criminal investigations, but refused to give details.
A spokesman said: "The MPS is liaising with a number of other UK police forces in relation to information which has been passed on to us regarding a number of criminal investigations. That information remains subject to assessment and for that reason we will not be discussing the matter in further detail at this time.
"We are not prepared to discuss at this time the number of investigations or details of any case."
Bellfield has been linked to several other crimes.
At the time of his conviction in June 2011, detectives said they believed Bellfield may have been responsible for around 20 attacks on women which were never solved.
These included the killing of Judith Gold, who was hit over the head in Hampstead, north London, in 1990, and Bellfield's schoolfriend Patsy Morris, 14, who was strangled on Hounslow Heath, west London, in 1980.
Anna Maria Rennie identified Bellfield as the man who tried to force her into a car in Whitton, west of London, when she was just 17 in October 2001. But the jury at Bellfield's 2008 trial for the murders of two other women could not agree and the charge was left on file.
Attempts for a retrial for attempted kidnap failed when Miss Rennie refused to attend court.
Bellfield was already in jail for the murders of Amelie Delagrange and Marsha McDonnell, and the attempted murder of Kate Sheedy, when he went on trial accused of killing Milly.
In 2008, he had been given a whole life term for murdering Ms McDonnell, 19, in 2003, and murdering Ms Delagrange, 22, and attempting to murder Ms Sheedy, 18, in 2004.
Milly was snatched from the street while on her way from school to her home in Walton-on-Thames, Surrey, in March 2002.
Her body was found in a wood in Yateley Heath, Hampshire - 25 miles from Walton-on-Thames.
Bellfield, 47, 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.
He was found guilty of abducting and killing Milly following a trial at the Old Bailey before he lost a bid in February 2012 to challenge his conviction at the Court of Appeal in London.
Surrey Police said a man in his 40s arrested on Wednesday was released without charge, after finding there was no evidence to support the accomplice allegation.