Police in Great Britain said they have identified new leads in the case of Madeleine McCann, the British girl who went missing in Portugal six years ago at the age of three.

Several persons of interest, as well as "both investigative and forensic opportunities" in the case, have been identified by Scotland Yard, authorities said.

Metropolitan Police said they were working with Portuguese police to determine the next steps, even though the missing girl's case is closed in the country.

"Our investigative review is ongoing and we are encouraged by the progress we are making," Metropolitan Police said in a statement, according to the BBC. "We are reviewing a significant number of documents and continue to identify potential lines of inquiry."

McCann was 3 years old when she vanished on vacation with her parents Kate and Gerry McCann and twin siblings in the Algarve region of Portugal. The girl's parents say they found Madeleine missing after having left the children in the home