London (CNN) -- After a renewed push for leads in the case of missing British girl Madeleine McCann, authorities in the United Kingdom are turning to Portuguese officials for help.
A letter sent by the Crown Prosecution Services to authorities in Portugal on Friday is requesting permission to conduct interviews in connection with the girl's 2007 disappearance from her family's holiday villa in the resort town of Praia da Luz.
Pedro do Carmo, the deputy national director of the Judiciary Police in Portugal, said Portuguese authorities have not yet received the letter, but he noted the latest lines in the Scotland Yard investigation focus on three people. Do Carmo declined to provide the nationalities of those three people, who he said have not been detained.
The development in the case comes roughly three months after new police sketches were released of potential suspects and UK police appeared in a TV appeal for information.
The program prompted a flurry of tips, and police in Portugal announced that same month that they would reopen the case.
Madeleine was 3 when she disappeared while she was on holiday with her family in June 2007. Her disappearance prompted headlines worldwide.
The two police forces' investigations have run in parallel since October. Do Carmo said Portuguese police have been in constant contact with authorities in the UK.
Detectives have been investigating a spike in break-ins in the area in the weeks before Madeleine disappeared, two of them in the same block where her family was staying.