At a press conference on Tuesday (October 9), officers from Scotland Yard also said that there could be 20 to 25 alleged victims in total of the late TV star.
Peter Spindler, commander of specialist crime investigations, said that police had recorded eight formal allegations so far against Savile, including two claims of rape.
Revealing that the claims spanned a period of 40 years, Spindler praised the alleged victims for "shining a light" on the alleged sexual abuse.
Entitled Operation Yewtree, the police inquiry will be run jointly with the children's charity NSPCC.
Police said today that the alleged victims were mainly girls aged between 13 and 16 at the time.
Peter Liver of the NSPCC said that the charity had received 17 calls to its helpline directly related to the allegations.
Police officers are also working with ITV, which featured the allegations on its Exposure documentary strand, and the BBC, which intends to launch its own investigation after the police inquiries after completed.
Scotland Yard has said that its assessment of the accusations against Savile remains a 'scoping exercise' at this stage, before it decides whether to launch a formal investigation.
> Jimmy Savile: BBC chairman says alleged behaviour 'inexcusable'
> Jimmy Savile was a creep, says Esther Rantzen