Despite finding no DNA connection to Madeleine, police are still trying to trace the car, a modern black Volvo registered in Belgium, used by the couple and the young girl when they left the cafe.

Officers have been unable to find the couple after checks on black Volvos with the letters VUV on the registration as this car was reported to have.

Yesterday, Belgian prosecutors confirmed a DNA sample taken from a restaurant where a woman reported seeing Madeleine McCann was not linked to the missing four-year-old.

Guilty feeling: the woman who says he saw Madeleine in the cafe

A police spokeswoman said the sample was from a man but said officers have not ruled out that Madeleine was present as he might have finished the bottle of drink.

A child therapist said she was "100 per cent sure" she saw the young girl at a restaurant in the Flemish town of Tongeren, not far from the Dutch border, on July 28.

Madeleine: the test proves she was not in Belgium

The witness said the girl was with a couple, a Dutch man and an English-speaking woman, who were acting strangely and not like "normal parents".

Sightings of four-year-old Madeleine have been reported all over Europe and further afield since she was snatched from her family's holiday apartment in Portugal on May 3.

Although so far none has proved positive, the young girl's mother said they helped her by demonstrating that people were still looking for her daughter.

Kate McCann told BBC Radio 4's Woman's Hour in an interview to be broadcast today: "We haven't had any news to the contrary that Madeleine isn't alive, and that's very important.

"And there have been many cases of children that have been found much later than this so again that's reassuring - so the hope's still there."

She and her husband Gerry faced the cameras again yesterday to affirm their belief that their daughter was still alive amid new speculation she was killed on the night she vanished.

Portuguese newspapers reported that detectives now suspected the young girl was not abducted, but died in her family's holiday flat in the Algarve village of Praia da Luz.

Blood specks found in the apartment are now being tested to see if they came from the missing four-year-old, reports claimed.

Sitting side by side, Kate and Gerry McCann spoke in subdued tones as they gave an interview to rebut suggestions that police now think Madeleine is dead.

The couple said they continued to "hope and pray" every day for the key breakthrough in the police investigation that would bring their daughter back to them.

Mr McCann, a cardiologist, said he and his wife "strongly believed" Madeleine was alive when she was taken from the apartment.

A waitress at the cafe where a witness claims she saw Madeleine drinking a milkshake

"We're not naive, but on numerous occasions the Portuguese police have assured us that they were looking for Madeleine alive."

Portuguese newspapers have suggested the police investigation is moving away from Robert Murat, at present the only official suspect or "arguido" in the case.

Chief Inspector Olegario Sousa, of the investigative Policia Judiciara (PJ), said it was the "official position" that the McCann family were not suspects.

Portuguese papers said yesterday that the McCanns would be re-interviewed by police shortly, but a family source said the couple had not been told about this.

The McCanns, who have remained in Portugal with their two-year-old twins, are gearing up for a bleak landmark this weekend - on Saturday it will be 100 days since Madeleine went missing on May 3.

So far there has been no major breakthrough in the case, and a second search of Mr Murat's home at the weekend apparently uncovered no new evidence.

Anglo-Portuguese Mr Murat, 33, has always strenuously maintained his innocence, and hopes the results of the search will prove he had no involvement in her disappearance.