Portuguese police announced on Friday they had identified a new suspect in their investigation into the disappearance of Madeleine McCann and friends said it was the 4-year-old's mother, Kate McCann.
McCann was questioned by police for more than 15 hours on Thursday and Friday and left the police station on Friday as her husband, Gerry, entered to be interviewed separately.
"Kate knows it's possible that she could get arrested," Justine McGuinness, a spokeswoman for the McCanns, said before the police announcement.
Police would give no name, in accordance with Portuguese secrecy laws, but friends of the McCanns had earlier said Kate McCann was about to become a suspect.
"All I can say is there is another formal suspect," police spokesman Olegario de Sousa told Reuters. "We always said new suspects or witnesses could come up, so this is nothing unusual."
McGuinness said Kate had told her that police found blood in a car hired by the couple but there was no confirmation it was Madeleine's blood. The car had been hired 25 days after Madeleine disappeared.
Police received results this week of forensic tests on evidence from various sites including the holiday apartment from which Madeleine vanished.
A British man emerged as the first formal suspect soon after Madeleine vanished on May 3.
Police had pursued a series of leads in their investigation, including that Madeleine may have been taken by a pedophile.
Under Portuguese law, declaring Kate McCann a suspect indicates police think she may have been involved in the crime but does not necessarily mean that she will be detained. She would have more legal protection than as a witness, including the right not to answer questions.
TSF radio reported that she would have to stay at a specific residence and would be unable to leave it without permission, meaning she would probably be unable to go back to England.
Hundreds of people across Europe contacted police offering help after the McCanns launched a massive publicity campaign to find their daughter.
Pictures of the girl have been posted across Europe at schools, airports and restaurants and the McCanns met Pope Benedict, who blessed a picture of Madeleine."Completely innocent"
Gerry rejected any suggestion of his wife's involvement on his blog (www.findmadeleine.com).
"The suggestion that Kate is involved in Madeleine's disappearance is ludicrous," he wrote. "Anyone who knows anything about the 3rd May knows that Kate is completely innocent. We will fight this all the way and we will not stop looking for Madeleine."
Madeleine vanished from a hotel room in the Praia da Luz resort in the Algarve while her parents dined with friends a short distance away.
Kate and Gerry decided to stay in Praia da Luz until the case is resolved, and have been going to a local church almost daily to pray for their daughter's safe return.
The only other suspect is a Briton living in Praia da Luz, who has not been arrested. His house has been searched twice.
A friend of the McCanns who spoke to Kate early on Friday said she was shocked then at the prospect of being declared a suspect.
"I did speak to Kate in the early hours of this morning and clearly she is stunned and disappointed," the family friend told the BBC.
British business tycoons and celebrities ranging from "Harry Potter" author J.K. Rowling to soccer stars have contributed to a reward for Madeleine's return.
(Additional reporting by Avril Ormsby, Henrique Almeida and Ruben Bicho)