The parents of missing Madeleine McCann say their faith that she will be found alive has not been shaken by speculation over her fate.
Forensic tests are being carried out on suspected traces of blood found in the Algarve apartment where four-year-old Madeleine was last seen on 3 May.
The BBC understands at least one British officer on the case is a specialist in locating murder victims.
But Gerry McCann said he had no reason to think his daughter was dead.
"We're not naive, but on numerous occasions, the Portuguese police have assured us that they were looking for Madeleine alive, and not Madeleine being murdered," Mr McCann said.
"And I don't know of any information that's changed that."
Sniffer dogs
Some Portuguese newspapers reported on Tuesday that detectives now suspect Madeleine died in the holiday flat in Praia da Luz on the night she disappeared.
A police spokesman told BBC News there were "some indications" she had not been alive when she had been taken but the possibility had not been discounted.
He added other people could be interviewed before the end of the week.
Mr McCann said he and his wife, Kate, from Rothley, Leicestershire, strongly believed their daughter had been alive when she had been taken.
It is believed detectives returned to the now-vacant apartment last week with at least one highly-specialised sniffer dog from Britain.
"We will work with them and continue to work with them for the breakthrough that we pray for every single day"
It is understood possible traces of blood were found during that search.
BBC correspondent Richard Bilton said it was believed the traces of blood were being assessed in a British laboratory with the results expected in a few days.
If tests confirm the find, police will look for a DNA match with Madeleine.
Mr McCann said he accepted that police needed to be thorough in all aspects of the investigation, including with his own family and friends.
Over the past 24 hours police have also re-examined up to 10 vehicles, including a hire car rented by Gerry and Kate McCann about five weeks after the disappearance of their daughter.
Kate McCann said they had an excellent relationship with the Portuguese police.
"We will work with them and continue to work with them for the breakthrough that we pray for every single day," added Mr McCann.
House search
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.
Police are also investigating a possible sighting of Madeleine at a restaurant in Tongeren, Belgium.
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