Madeleine McCann who vanished while on a family holiday in Portugal five years ago may be alive, UK police say.
London's Metropolitan Police said on Wednesday they were still investigating the disappearance of the girl, who vanished shortly before her fourth birthday in May 2007.
Detective Chief Inspector Andy Redwood says he is leading a team of more than 30 police officers who are focusing on the case. Police said they believe there is a possibility she is alive but also have to consider that she may be dead.
Portuguese police closed their investigation in 2008 but Scotland Yard says it wants the case reopened.
Redwood says his officers are reviewing all the evidence that has been gathered so far by British and Portuguese police and by private investigators hired by McCann's parents.
He says he has made seven visits to Portugal and is working closely with Portuguese police officers. He also has regular contact with the missing girl's parents, Kate and Gerry McCann.
Forensic evidence of the sequence of events around her disappearance shows that there are moments when she could have been snatched by criminals.
Police will release a new image of the girl, who would now be nine years old if she were alive.
There has been no reliable indication of what might have happened to the girl despite numerous reported sightings from around the world.
Her disappearance has drawn global media attention, partly because her parents were at one point questioned as suspects by the Portuguese police. They were cleared of any part in the disappearance.
Kate and Gerry McCann have since headed a campaign to keep the case in the public eye, publishing a book and appearing on the Oprah Winfrey Show to tell their story.
UK police said the investigation has cost STG2 million ($A3.14 million) so far.