( CNN ) -- Police in Portugal are reopening the case of Madeleine McCann , a British girl who was 3 years old when she disappeared while on vacation there with her family in 2007 , prosecutors in Portugal said Thursday . This follows the discovery of new lines of inquiry after an internal review of the original Portuguese investigation , London 's Metropolitan Police said . Madeleine 's parents , Kate and Gerry McCann , have been briefed on the decision , the UK police statement said . For parents of the missing , does hope spring eternal ? Mystery has surrounded Madeleine 's disappearance from her family 's holiday villa in the Portuguese resort town of Praia da Luz for the past six years . A unit from the Metropolitan Police has also been working on a new investigation . It issued fresh suspect drawings in the case last week , along with a televised appeal for information , which prompted a flood of calls and e-mails from the public . Neither her parents nor the detectives investigating her case have given up on one day finding the little girl from Leicestershire , England . The two police forces ' investigations will run in parallel and at the moment are following separate new leads , the Metropolitan Police said Thursday . The Portuguese and UK police `` have a shared determination to do everything possible to discover what happened to Madeleine , '' said Assistant Commissioner Mark Rowley of the Metropolitan Police . 1,000 responses to new police appeal . But , he cautioned , while the latest developments are welcome , the dual investigations are at relatively early stages and much work remains to be done . `` This new momentum is encouraging , but we still have a way to go , and as with all major investigations , not all lines of inquiry that look promising will yield results , '' Rowley said . UK detectives have been trying to reconstruct exactly what happened on the night of May 3 , 2007 , when Madeleine disappeared from the villa while her parents dined at a nearby restaurant . The girl was just days shy of her fourth birthday . The discovery last week of a blond girl aged 5 or 6 living with a Roma couple in Greece who proved not to be her biological parents thrust the issue of missing children into the spotlight . Kate and Gerry McCann told UK media last week that the news from Greece gave them `` great hope '' that their own daughter , who would now be 10 years old , could be found alive . About 10 cases of missing children around the world are `` being taken very seriously '' in connection with the Greek girl 's case , including children from the United States , Canada , Poland and France , a spokesman for a Greek children 's charity said . Two callers name man in new sketches . CNN 's Lindsay Isaac and Alexander Felton contributed to this report .
NEW : `` This new momentum is encouraging , but we still have a way to go , '' says UK officer . Portuguese police are taking another look at Madeleine McCann 's disappearance . The 3-year-old vanished from her family 's Portuguese holiday villa in May 2007 . The UK and Portuguese investigations currently have separate leads , officer says .