LONDON (AP) -- British police say they are investigating new leads in the case of Madeleine McCann, the Briton who disappeared six years ago in Portugal at the age of three.

Scotland Yard said it has identified several "persons of interest" and "both investigative and forensic opportunities" in the case. The force said Friday its work is under way to support police in Portugal, even though they have closed their investigation into the disappearance.

McCann vanished from her family's vacation home in Portugal's Algarve region on May 3, 2007, days before her fourth birthday. The case has generated intense media interest in Britain.

British police launched Operation Grange in 2011, to try to solve the puzzle.

Detective Chief Superintendent Hamish Campbell said Friday officers have been encouraged by the progress made so far.