Kate McCann could be charged over the disappearance of four-year-old daughter Madeleine according to her lawyer.
Mrs McCann, 39, has been made a formal suspect. She is reportedly being asked further questions linked to DNA tests on samples taken from car the family hired over three weeks after Madeleine's disappearance.
Detectives suggested traces of Madeleine's blood were discovered in the vehicle. Tests have also been carried out on traces of blood found in the apartment where Madeleine went missing on May 3.
Her lawyer, Carlos Pinto de Abreuhas, has reportedly told Kate that she may face charges.
The family spokesperson said Portuguese police have named Kate McCann as an " arguido'' - a formal suspect. The arguida status allows police to put questions to Madeleine's mother while giving her the legal right to remain silent.
The family spokesperson said: "Just before the session ended last night, they made it clear they had some further questions to ask which would require her to be in arguido status rather than just witness status."
Mrs McCann is said to be shocked at the development. She looked drawn and tired when she left the police station early this morning.
The spokesperson said: "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."
Gerry McCann is expected to be questioned this today.
Writing on his blog today Mr McCann said: "The suggestion that Kate is involved in Madeleine's disappearance is ludicrous. 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."
The McCanns have consistently denied any part in Madeleine's disappearance. No charges have been brought.
The development comes amid reports that arrests could be imminent following a forensic breakthrough.
Experts at the Forensic Science Service in Birmingham have spent the past month analysing samples taken from the McCanns' holiday apartment in the Algarve resort of Praia da Luz using Low Copy Number analysis.
The technique allows scientists to find a genetic fingerprint from a tiny sample by "growing" it into extra copies that may be repeatedly tested.
Information from the Forensic Science Centre in Birmingham, where they had been testing swabs taken from the holiday flat where Madeleine was last seen, has reportedly been returned to Portugal.
The McCanns' spokesperson, Justine McGuinness said: "Kate and Gerry are happy to help the police in their investigations to find their daughter Madeleine, as they have been since she was taken."
In her own brief statement, before entering the police station yesterday, Mrs McCann said: "I miss Madeleine so much. Gerry and I want to appeal again to the person or people who took her or know who took her to do the right thing."
Also waiting for details of the forensic tests is the only official suspect in the case, 33-year-old Anglo-Portuguese ex-pat Robert Murat.
He strenuously denies any involvement in Madeleine's disappearance and believes the Portuguese authorities will shortly clear him formally.