DNA test results from a restaurant in Belgium have not provided a match with missing four-year-old Madeleine McCann.
The DNA - taken from a drink bottle and straw after a girl was seen with a man at a cafe - matched that of a man, prosecutors in Tongeren town said.
It "doesn't mean that the presence of Maddie is excluded", they added.
Meanwhile, suspected traces of blood from the Algarve apartment where Madeleine was last seen are being tested in Birmingham by UK scientists.
It is believed the evidence was found during a search involving at least one sniffer dog from Britain.
Madeleine's parents say they still have faith she will be found alive.
The Belgian DNA tests were on a strawberry-flavoured milk drink bottle and a straw.
Police were contacted after a girl suspected of being Madeleine was spotted at a roadside cafe with a Dutch-speaking man aged around 40 and an English-speaking woman of around 25.
Prosecutors added that "the man accompanying her may have drunk from the bottle" and that it was strange the couple involved had not come forward to be excluded from the police inquiry.
A prosecution official said although the DNA had not produced any matches in databases, the investigation remained open.
"We are seeing what tip-offs come in, although to date we have not had anything that has led to concrete results."
Some Portuguese newspapers reported on Tuesday that detectives now suspect Madeleine died in the holiday flat in Praia da Luz on 3 May - the night she disappeared.
Detectives in Portugal are refusing to comment officially on those reports.
A police spokesman told BBC News there were "some indications" she had not been alive when she was taken, but the possibility had not been discounted.
He said other people could be interviewed before the end of the week.
If tests in Birmingham confirm the find of traces of blood, police will look for a DNA match with Madeleine.
Kate McCann told BBC Radio Four's Woman's Hour on Wednesday she had no reason to think her daughter was dead.
She and her husband, Gerry, from Rothley, Leicestershire, believed their daughter was still alive, she said.
"We haven't had any news to the contrary - that Madeleine isn't alive - and that is very important.
"They have been many cases of children that have been found much later than this and that is reassuring, so the hope is still there."
A suspected sighting of Madeleine took place at this restaurant
Mrs McCann said the family had maintained a good relationship with Portuguese police and she accepted detectives needed to be thorough in all aspects of the investigation, including with her own family and friends.
Over the past 48 hours, police have also re-examined up to 10 vehicles, including a hire car rented by the McCanns about five weeks after the disappearance of their daughter.
"We have just got to think to ourselves that we need the investigation to be thorough - we welcome that," Mrs McCann said.
However, she said recent speculation about reported sightings of Madeleine and the circumstances of her disappearance had been "upsetting" and did not help the investigation.
A second search of the home of suspect Robert Murat, 33, in the Portuguese resort in recent days found no new evidence.
Two of the vehicles re-examined on Monday were a car and a van used by Mr Murat, the only declared suspect in the case.
On Monday night, the vehicles were returned to the Murat family villa, which is owned by Mr Murat's mother.
Publicly the police have not commented on the results of the weekend search but the BBC understands it revealed nothing to link Mr Murat to Madeleine.
Mr Murat was declared a suspect 10 days after Madeleine was last seen but has strenuously denied any involvement in her disappearance.