Fourteen-year-old Alice was last seen on August 28, when she was spotted on CCTV by the Grand Union Canal in west London.
Detective Superintendent Carl Mehta, from the Met’s Homicide and Major Crime Command, named Arnis Zalkalns as a suspect after he was seen on CCTV around the tow path where Alice went missing.
Supt Mehta said that the 41-year-old had been convicted of murder in his country and was also arrested on suspicion of indecent assault in the Ealing area in 2009.
The officer said: “The conviction was in 1998 and he served a custodial sentence of seven years.”
Supt Mehta said no further action was taken against Zalkalns over the indecent assault allegation, which involved a 14-year-old girl.
He also insisted police have no evidence suggesting Alice has come to harm. “This is not a murder inquiry in the sense that we don’t have any evidence or information to say that Alice is not alive,” Mr Mehta said.
Zalkalns was seen on CCTV cycling along Brentford Lock at 4pm on August 28, 15 minutes after Alice walked the route.
Detectives believe he is likely to have seen Alice as they were both going north along the canal towpath. Since Zalkalns was last seen at his home in Ealing on the evening of Wednesday September 3 he has not accessed his bank account or used his mobile phone. His passport was left at his house.
His friends and family have told police that his disappearance is out of character.
Supt Mehta said Scotland Yard was liaising with authorities in Latvia but Zalkalns is not thought to be wanted by police there.
Forensic searches are being carried out at his home address. Mr Mehta said it was his understanding that UK authorities had no record of Zalkalns’ murder conviction.
Police had been told about the conviction in the “last few days” but were unable to provide further details at this stage, he added.
Zalkalns is thought to have come to the UK in 2007 and lives with his partner and their young child.