Al Gore has been questioned by police over renewed allegations that he sexually assaulted a massage therapist.
Detectives in Portland recently reopened an investigation into claims by Molly Hagerty that the former US vice-president groped her during a massage session in his hotel suite four years ago.
Local news outlets reported that police interviewed Mr Gore a week ago in San Francisco, questioning him over Miss Hagerty's claims about his unwanted sexual advances.
His spokesman has said he "unequivocally and emphatically denied" the accusations.
Portland police did not give reasons for the decision to open the investigation, but it followed soon after the masseuse made new claims in a tabloid magazine about her alleged ordeal.
A spokesman for Mr Gore, now a champion for action on climate change, said he "welcomed" the police announcement as "further investigation into this matter will only benefit" him.
Police had earlier said they considered the case closed because there was insufficient evidence but they had said they might reconsider if any new information came to light.
Miss Hagerty, 54, was pictured in the National Enquirer holding a bag containing what she claims are a pair of her trousers that may have been stained by Mr Gore, who wore only an open bathrobe as he received the massage.
She alleges Mr Gore groped and kissed her in an aggressive attempt to have sexual intercourse.
Interviewed by detectives in 2009, she said she had told Mr Gore he was behaving like a "crazed sex poodle".
Telegraph Media Group Limited