Police have refused to comment on reports that blood was found in the apartment where Madeleine McCann was sleeping before she disappeared.
If scientific tests confirm that the traces found last week are blood, scientists will carry out further tests to find out if it matches the girl's DNA.
The discovery was made by detectives when they searched the apartment in Praia de Luz, in Portugal, last week with specially-trained British sniffer dogs.
The parents of the missing gir have said they believe that their daughter was alive when she disappeared.
Gerry McCann also played down reports that police now believe she may have died in an accident.
Mr McCann said it was difficult to have the police investigating them, detectives are still looking at their car, but he said the couple expected to be treated the same way as anyone who had been around them.
Meanwhile in Lisbon, police probing Madeleine's disappearance said they envisaged new hearings in the coming days but they refused to confirm or deny that police are now considering the possibility that her death had been accidental.
Elsewhere, Belgian police are carrying out DNA tests on a drinks bottle used by a girl resembling the missing child.
They are investigating a possible sighting of the missing four-year-old in the Flemish town of Tongeren, near the Dutch border.
Click here for a timeline of the events around Madeleine's disappearance
