Madeleine McCann's parents were today said to be "very, very pleased" with Scotland Yard's review of their daughter's disappearance, as it emerged detectives have identified "more than a handful of people of interest" in the case.

Detective Chief Superintendent Hamish Campbell said the review, dubbed Operation Grange, has identified "both investigative and forensic opportunities" and said the people of interest could be explored further, if only to be eliminated.

Madeleine's parents Kate and Gerry, who spoke earlier this month about how they were encouraged by the review, today repeated their support for it.

Their spokesman Clarence Mitchell said: "Kate and Gerry remain very, very pleased with the work that Scotland Yard are doing and have been encouraged by Operation Grange from the day it began.

"Beyond that, they simply will not comment on what are police operational matters."

Madeleine, who was then nearly four, disappeared from her family's holiday apartment in Praia da Luz in Portugal's Algarve on May 3 2007, as her parents dined at a tapas restaurant with friends nearby.

Operation Grange, conducted by Scotland Yard's Homicide & Serious Crime Command, was launched in May 2011.

Today Mr 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."

As they marked the sixth anniversary of Madeleine's disappearance earlier this month, Mr and Mrs McCann said they were encouraged by Operation Grange, and said 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."

Mrs McCann, who recently returned to Portugal, said their family, including twins Sean and Amelie, now eight, had found a "new normality'' since Madeleine's disappearance.

She encouraged anybody with any information to contact police, added: "I think to encourage everybody, it's six years on, but the way the Met review is going is really positive and with that, new hope.

''The search goes on, in a major way.''