Portuguese detectives will re-interview the parents of missing British girl Madeleine McCann as the search continues into its fourth month, a friend of the family said Thursday.

Madeleine's parents, Kate and Gerry McCann, will speak with police separately, family friend Clarence Mitchell said.

Kate McCann, the mother of missing four-year-old Madeleine McCann, displays a poster for her missing daughter during a June news conference in Morocco.
(Abdeljalil Bounhar/Associated Press)

Kate McCann was to speak with police Thursday afternoon, while Gerry McCann's interview was set for Friday.

The four-year-old vanished May 3 from a vacation apartment in Praia da Lux, a town on Portugal's southern Algarve resort coast.

Madeleine was sleeping in the apartment along with her two-year-old twin siblings while her parents ate dinner in the hotel's restaurant 50 metres away. The McCanns said they checked on their children regularly.

The McCanns have remained in Portugal since the disappearance, running an internet search campaign and leaving occasionally to visit countries where people had reported seeing a girl matching Madeleine's description and to raise awareness about her disappearance.

The pair have been interviewed by police previously. Detectives have stressed that they are interviewing the parents as witnesses, not suspects, in the probe.

Portuguese media have repeatedly suggested the McCanns were involved in Madeleine's disappearance, allegations police have dismissed.

Media reports claim the interviews were prompted by new forensic evidence in the case.

Detectives were awaiting DNA results at the end of August, and a senior police officer said they had a "positive feeling" about the search.

The McCanns have repeatedly said they believe their daughter is still alive.

With files from the Associated Press