Police are looking for a missing Latvian man in connection with the disappearance of 14-year-old Alice Gross.
Arnis Zalkalns, 41, is known to travel on the same stretch of the Grand Union Canal where the schoolgirl was last seen, and has not been seen himself for almost two weeks.
Scotland Yard said his disappearance is 'completely out of character' and are probing whether he knew Alice.
Mr Zalkalns, a Latvian national who lives in Ealing and works as a builder, has a partner and a child.
He was last seen at his home on the evening of Wednesday, September 3.
It is believed he left home the following day, and he would normally meet a friend to cycle to work but did not turn up.
His normal route to work would take him along the Grand Union Canal in west London - near to where Alice went missing on the evening of Thursday, August 28.
Detective Superintendent Carl Mehta, of the Met's homicide and major crime unit, said: "It is completely out of character for Arnis to go missing. His family is very worried about him. I am asking for anyone who has seen him, or knows where he is to get in touch.
"Given the time that Arnis was last seen, and that he travels to work along a similar route to the one we know Alice took on August 28,
"I am really keen to speak to him. At this stage, we simply want to speak to him, as he may well have important information that can help our search for Alice."
He added: "I would stress that based on what we know now there is no evidence to suggest that Arnis and Alice knew each other. This continues to be a fast moving investigation, and this is one of a number of lines of enquiry that we are urgently looking into."
It comes as detectives prepared to make a new TV appeal tonight as the search for the schoolgirl from Hanwell continues.
Officers say that despite numerous appeals police have no confirmed sightings of her since then and her white iPhone 4s has not been used since she sent a last text to her father earlier the same day.
Police say a couple had come forward to say they saw Alice's rucksack on the evening she went missing on a footpath that runs besides the River Brent between Hanwell Bridge and the Grand Union Canal.
The couple did not move the bag which was close to where two builders saw it on the following day in a patch of undergrowth.
The bag contained the Van shoes Alice was wearing when she left home earlier in the day to go for a walk.
Detective Chief Inspector Andy Chalmers, who is leading the inquiry, said he was keen to trace Alice's phone or anyone else who may have moved or found Alice's bag.
He added: "Alice's family are devastated. They think about her constantly. If you have any information that can help us bring Alice back to her family, no matter how small or trivial it may seem to you, please call us."
Anyone with information should call 020 8358 0100, or call Crimestoppers anonymously on 0800 555 111.