The latest alleged victim spoke to police after talking to ex-Vogue model Natasha Prince, who accused Blaine of raping her in 2004.
Ms Prince told The Sunday People: "After I told my story, a British ex-model got in contact with me. I got really emotional and started crying."
Prince alleges that Blaine drugged and anally raped her at a private home in the Chelsea section of London in the summer of 2004, The Daily Beast reported.
Blaine, through his attorney, denied the allegations but said he will cooperate fully with the investigation because "he has nothing to hide."
"Officers from the Met's Child Abuse and Sexual Offences Command are investigating an allegation of rape," Scotland Yard said in a statement.
"The allegation was reported to police on 17 November 2016 by a woman who alleged she was raped at an address in Chelsea in June or July 2004 when she was aged 21. There have been no arrests at this stage and inquiries continue."
Speaking about the latest allegation, Scotland Yard told The Sunday People: "The Metropolitan Police Service received an allegation of sexual assault on Monday, 23 October 2017.
"The offence is reported to have happened against a woman in New York between May and June 1997. Specialist officers are supporting the victim."