The 59-year-old former artistic director of London’s Old Vic theatre was interviewed in the US under caution in May.
Scotland Yard refused to identify the subject of the investigation but confirmed that “a man was voluntarily interviewed under caution in America by officers from the Met’s Complex Case Team”.
“He was not arrested,” a spokesperson added. “Inquiries are ongoing.”
Spacey was first named in a report by American website Variety.
The alleged assaults are said to have taken place in Gloucester and London between 1996 and 2013.
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The first complaint, relating to an alleged offence in Lambeth in 2008, was referred by the City of London Police to the Metropolitan Police on 1 November 2017.
A second alleged victim went to police on 20 November that year in relation to a sexual assault in Lambeth in 2005.
The third, made on 13 December 2017, concerns an allegation of sexual assault in Westminster in 2005.
Between February and April 2018 three further complaints were received, relating to alleged offences in Westminster in 1996, Lambeth in 2008 and Gloucester in 2013.
The alleged victim has dropped a civil lawsuit against the actor but Spacey still faces criminal charges of indecent assault and battery, which is a felony. If convicted, the Hollywood star faces a maximum of five years in prison and would be required to register as a sex offender.
Sexual misconduct allegations were first brought forward in October 2017 at the height of the #MeToo movement, which centred on allegations against former Hollywood producer Harvey Weinstein.
Actor Anthony Rapp said that Spacey made sexual advances towards him about 31 years ago during a party. At the time, Rapp was 14 and Spacey was 26.
In response, Spacey said he did not remember the alleged incident, but apologised for his “deeply inappropriate drunk behaviour”.
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