BRITISH police are opening their own investigation into the 2007 disappearance of toddler Madeleine McCann in Portugal and have identified 38 "persons of interest" across Europe.

A two-year review of the original Portuguese investigation, which is officially closed, had resulted in some new evidence, said Detective Chief Inspector Andy Redwood of Scotland Yard, the officer in charge of the probe.

Police also still believe that Madeleine, who was three when she disappeared, may be alive, he said.

"We have identified 38 persons of interest from a number of European countries. Twelve of those people are UK nationals who we believe were in Portugal at the time Madeleine disappeared," Insp Redwood said.

"The inquiries that we seek to undertake will be to understand more about what role if any they played in Madeleine's disappearance."

Neither Madeleine's parents Gerry and Kate, nor the friends who were having dinner with the McCanns when she disappeared, were among the suspects, he said.

The McCanns said it was a "huge step forward" in their ongoing search for their daughter.

The couple launched a global campaign to find Madeleine after she vanished from the family's holiday flat in Praia da Luz on Portugal's south coast in May 2007, while they were eating dinner nearby.

Pictures of the smiling blonde girl were plastered on newspapers, posters and websites across the world, although numerous possible sightings came to nothing.

Scotland Yard said they believed she was still alive.

"There is no clear definitive proof that Madeleine McCann is dead and so on that basis I still genuinely believe that there is a possibility that she is alive, and so I would ask the public to continue to look for her," Insp Redwood said.

Since the ongoing review was launched in 2011, British police have gathered more than 30,000 documents, visited Portugal 16 times, carried out new witness interviews and generated new theories.

"The review has given us new thinking, new theories, new evidence and new witnesses," Redwood said.

"That has given us the ability to see this case with fresh eyes, and through that bring out new, genuinely new, lines of inquiry."

He added: "I believe critically that this is an important moment for Madeleine."

In April, Portuguese authorities said they had no new evidence that would give them cause to reopen their own inquiry.

But Insp Redwood said his team had a "positive" relationship with their Portuguese colleagues and had requested their help through official channels in chasing up new leads.

Of the 38 suspects, 12 are British and were all in Portugal at the time of Madeleine’s disappearance.

They are now believed to be back in the UK, still in Portugal as well as three other unnamed European countries.

The suspects do not include the toddler’s parents Kate and Gerry McCann nor their friends they were holidaying with when she went missing.

The team has gathered 30,500 documents with at least 3800 “actions” that need to be taken including following leads.

Police also have new witnesses but have declined to expand on who they are or where they are from.

Kate and Gerry McCann — who have fronted a high-profile international campaign to find their daughter — have been kept up to date on developments.

Spokesman for the McCanns, Clarence Mitchell said: “Kate and Gerry warmly welcome this shift in the Metropolitan Police emphasis. They see it as a huge step forward in establishing what happened and hope that it will lead to bringing to justice whoever was responsible for Madeleine’s abduction.”

Detective Redwood’s assumption that Madeleine could be alive is based on the fact there was no proof that she was dead.

Police would last night not elaborate on where the other suspects came from including whether any were from Australia.

As previously reported, police had once been chasing a lead from a British businessman in Barcelona who was approached by a woman with an Australian accent who told him said she was waiting to take delivery of “my new daughter”.

The woman, who also spoke fluent Spanish, was reportedly agitated and left the marina area of the Spanish city when she released she had approached the wrong man.

The incident took place three days after the disappearance of the toddler but was not reported to police for at least six weeks.

Since that report back in 2009 there has been numerous alleged sightings of her in Australia.

Police were never able to trace the identity of the woman.

One theory chased by both British, Portuguese and Spanish police was that Madeleine was abducted and taken out to sea on a yacht.

British police have also been in touch with a number of European countries about the so-called "persons of interest".

"Over the coming months we will be conducting assertive enquiries, with the assistance of host countries, to establish more information about the individuals concerned and any potential involvement," the Scotland Yard statement said.

Police have regularly released computer generated images of what she may look like now - Madeleine would have celebrated her ninth birthday last month.

And the McCanns, who themselves were suspected at one point in the Portuguese investigation, have never given up hope of finding her alive.

On the fifth anniversary of Madeleine's disappearance last month, Gerry McCann said: "We're probably more hopeful now than at any point in that last five years."