PRAIA DA LUZ - The mother of missing British four-year-old Madeleine McCann will be formally declared a suspect on Friday, a spokeswoman for the family said.

The sudden shift in the investigation came after authorities received forensic evidence recovered from the holiday apartment in the Algarve where Madeleine vanished on May 3.

Since her disappearance, Madeleine's parents have campaigned relentlessly to draw attention to the case. Their efforts led to a meeting with Pope Benedict in Rome who blessed a picture of their daughter.

"She will be formally declared a suspect," said Justine McGuinness, a spokeswoman for the McCanns. Both Kate and her husband Gerry are expected to be interviewed separately by police on Friday.

Under Portuguese law a suspect has more legal protection than a witness, including the right not to answer questions. A witness must answer all questions put forward by police or possibly face legal action.

However, Kate McCann will be more closely monitored by police. On Thursday, she was questioned by police for about 11 hours at a police station in the Algarve. Her husband Gerry is expected to be questioned by police on Friday.

A friend of the McCanns who spoke to Kate in the early hours of this morning said she was stunned and disappointed at being declared a suspect.

"I did speak to Kate in the early hours of this morning and clearly she is stunned and disappointed. Disappointed, not only to be at this stage a suspect, but I think (at) the realisation that they are not actually looking for Madeleine," the family friend told the BBC.

"She sounded disappointed, calm, disappointed, tired."

A Briton living in Praia da Luz had until now been identified by police as the only suspect in the investigation and his house has been searched twice.

British business tycoons and celebrities ranging from "Harry Potter" author J.K. Rowling to soccer stars have contributed to a reward for her return.