Portimao, Portugal - The mother of missing British toddler Madeleine McCann will be questioned again on Friday morning by police investigators following 11 hours of questioning the day before, a police source told the Portuguese news agency Lusa.

Kate McCann was questioned for nearly 11 hours on Thursday by police investigating the disappearance of her then three-year-old daughter on May 3 from the vacation apartment they were staying at in the seaside resort of Praia da Luz.

Her husband Gerry was also due to be questioned on Friday.

Emerging from the police station after the 11 hours of questioning, Kate McCann's lawyer said she was still considered a witness and the investigation was continuing.

Portuguese laws severely restrict what those privy to an investigation may say publicly.

The Portuguese police have confirmed that they received on Wednesday part of the forensic laboratory results of traces of blood found in the room in the apartment where Madeleine had been sleeping before she disappeared.

The police have made no statement as to what the lab results showed, or whether the blood belonged to the child or to someone else.