British detective have identified a "good number" of potential suspects in their hunt for missing Madeleine McCann, a top detective has said.

The Metropolitan Police was asked by the Prime Minister to join the search for the child, who went missing on May 3 in Praia da Luz in 2007 during a family holiday.

She would now be 10 and her parents insist the search for her is very much ongoing.

In a statement on Friday morning, Detective Chief Superintendent Hamish Campbell said: "The purpose of the review was to look at the case with fresh eyes and there is always real benefit in doing so.

"The review has further identified both investigative and forensic opportunities to support the Portuguese.

"There is more than a handful of people of interest which could be explored further if only to be eliminated.

"The key things are to investigate the case and our work is happening to support the Portuguese."

Campbell, who is about to retire from the force, also spoke about the case in an interview with the Evening Standard.

He told the paper the Met squad had done a “fantastic” job in identifying “further investigative and forensic opportunities.”

“We have to ask ourselves why are cases unsolved and, on many occasions, we find we passed the suspects by already and the suspect sits within our system,” he said.

The detective also said Madeleine could still be alive, adding: "You cannot exclude it."

As they marked the sixth anniversary of her disappearance earlier this month, her parents Kate and Gerry McCann said they remained hopeful as ever as Operation Grange continued, and that police seemed "more determined than ever".

''In many ways things haven't changed and you could argue that, with the Met review two years in, we are actually in a better place because so much more information has been collated and lots of pieces of the jigsaw have been filled,'' said Mr McCann.

The couple's hope was further reinforced by the recent discovery of Amanda Berry, Gina DeJesus and Michelle Knight in Ohio, a decade after they went missing in separate incidents.

When the women were found, the McCanns said the rescue of the women "reaffirmed" their hope of finding their daughter, which had never diminished.

"Their recovery is also further evidence that children are sometimes abducted and kept for long periods," they said in a statement.

"So we ask the public to remain vigilant in the ongoing search for Madeleine."