The mother of missing four-year-old Madeleine McCann has been formally declared a suspect by the Portuguese police, a family spokeswoman has said.
The BBC has learnt that the move was linked to bloodstains allegedly found in Kate and Gerry McCann's hire car.
Mrs McCann has arrived for her second police interview in 24 hours. Mr McCann is expected there shortly.
Her status as "arguida" allows the authorities to put certain questions and gives her the right of silence.
The couple, from Rothley, Leicestershire, deny any involvement in Madeleine's disappearance on 3 May.
Family spokeswomen Justine McGuinness told the BBC why the police were now treating Mrs McCann as a suspect.
She said: "They believe they have evidence to show that in some way she's involved in the death of her daughter, which of course is completely ludicrous. They have suggested that blood has been found in a hire car that they hired 25 days after Madeleine was taken."
Meanwhile friends of the family said that Mrs McCann has been told by her lawyer that she could be charged in connection with the disappearance of her daughter.
A large number of journalists and members of the public were outside the police station in Portimao, Portugal, to watch Mrs McCann arrive by car.
She entered the building to the sound of a few whistles and some shouts in Portuguese from the waiting crowd.
One British tourist shouted: "We believe you, Kate."
It is understood that Portuguese police have told Mrs McCann, 39, they have 22 questions they want to ask her during today's interview although they have not told her what they are.
Ms McGuinness said: "Just before the session ended last night, the police made it clear they had some further questions to ask which would require her to be in arguida status rather than just witness status."
The spokesman added: "She is shocked and surprised in several ways. First of all that such an accusation could be made against her.
"And obviously she is concerned that such a line of investigation can become a distraction from further attempts to find Madeleine."
Madeleine disappeared from the family's holiday apartment while her parents were eating in a nearby restaurant.
Madeleine was last seen on 3 May
Mrs McCann had previously been interviewed before by police the day after Madeleine disappeared, but yesterday was the first time her lawyer had been present.
She was questioned as a witness until after midnight on Thursday. Police have previously said the McCanns are not suspects.
In a statement released before her interview yesterday, she appealed to her daughter's abductors, saying: "It is not too late - please let her go or call the police."
She said: "We came to Portugal an ordinary family of five. We just want to know what happened on 3 May and want to be able to go home one family, reunited."
Mrs McCann will become the second formal suspect in the case. The first was Robert Murat, a British man living locally. He has not been arrested or charged.
Mrs McCann's husband Gerry, originally from Glasgow, is expected to be questioned on Friday afternoon about Madeleine's disappearance from an apartment in Praia da Luz, Algarve. It's is not known whether he too will be questioned as a suspect
Samples, including suspected traces of blood, have been recovered from the McCanns' holiday apartment.
The UK's Forensic Science Service has spent the past month analysing them.
Portuguese police spokesman Chief Inspector Olegario Sousa said partial results from tests had been received, but would give no further details.
Last week, the McCanns launched a libel action against a Portuguese newspaper which reported that "police believed" the couple killed Madeleine, with the paper suggesting she may have died in an accident.
A public statement from the director of police followed, saying neither Kate nor Gerry McCann had ever been viewed as suspects.
The McCanns have travelled extensively through Europe to raise awareness of the search for their daughter.