The Metropolitan Police has received a report of an alleged sexual assault in 2003 in the wake of media allegations about Russell Brand.
Officers did not name Brand, but said they were in contact with the woman and were "providing her with support", BBC reports.
Over the weekend the comedian and actor was accused of rape and sexual assaults between 2006 and 2013, which he denies.
Following the allegations, upcoming shows on Brand's live tour have been postponed, the promoter confirmed.
On Monday one of the women whose allegations against Brand were part of the investigation by The Times, The Sunday Times and Channel 4 Dispatches told the BBC the comedian's behaviour had been an "open secret", and described his denials as "laughable".
In a statement the Met said it was aware of the media allegations and continued: "On Sunday, 17 September, the Met received a report of a sexual assault which was alleged to have taken place in Soho in central London in 2003."
The force first spoke to the Sunday Times on Saturday, it said, and has since made further approaches to the newspaper and Channel 4 to ensure anyone who believes they are a victim of a sexual offence "no matter how long ago it was" knows how to report it to the police.
The force has not said they have begun a criminal investigation or that any arrests have been made.
He has denied all claims of misconduct, saying he is the subject of "a coordinated attack" involving "very serious allegations that I absolutely refute."
The former TV and radio presenter, who now posts videos online about spirituality and politics, said his relationships have been "always consensual". On Monday, Brand did not appear for his regular livestream on video platform Rumble.