Detectives suggested to Mrs McCann during questioning on Thursday that traces of the four-year-old's blood were found in a car the family leased 25 days after she went missing from their holiday apartment, said a family friend Justine McGuinness.

Mrs McCann told detectives there was "no way" Madeleine's blood could have been found inside the car and she continues to protest her innocence, Ms McGuinness said.

Mrs McCann on Friday returned to the Portimao police station for further questioning, during which she was declared an arguida - someone who has not been arrested or charged but is being treated by police as more than a witness.

She arrived at the station shortly after 11 am, barely more than 10 hours after she emerged from a marathon interview with detectives last night. Mrs McCann walked straight from her car to the building without talking to reporters gathered outside.

“They [the police] believe they have evidence to show that in some way she [Mrs McCann] was involved in the death of her daughter,” Ms McGuinness told the BBC. “They have suggested that because blood has been found in a hire car that was hired [by the McCanns] 25 days after Madeleine was taken. They made a series of ridiculous allegations and she was absolutely horrified. Kate is a loving mother to her children and would never hurt them. There is a fear that she may be arrested for a crime that we have no idea was actually committed by anybody and that certainly she did not commit.”

Ms McGuinness said Mrs McCann was asked a lot of detailed questions yesterday, but none of them was about the events of May 3, the day that Madeleine disappeared. Lita Gale, a Portuguese lawyer, said charges were more likely once a witness was declared an arguido - or arguida in the case of a woman but cautioned against speculation about the nature of any possible charges.