(CNN) -- Belgian police have confirmed to CNN that a young girl spotted in Belgium last week was not missing Madeleine McCann after conducting DNA tests on a straw and bottle used by the girl.
Madeleine's parents Gerry and Kate say they believe she is still alive.
The British four-year-old disappeared from a holiday apartment in the Portuguese resort of Praia da Luz on May 3.
A woman reported the sighting of a young girl apparently matching Madeleine's description last week in a roadside cafe in the eastern Belgian town of Tongeren.
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."
Madeleine's parents, Kate and Gerry McCann, have campaigned internationally to secure the safe return of their daughter, including having a meeting with Pope Benedict XVI and securing support from soccer star David Beckham.
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 girl's mother said they helped her by demonstrating that people were still looking for her daughter. ( Watch how the reported sighting turned out not to be Madeleine »)
In an interview to be broadcast on the BBC on Wednesday, she says: "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 said on Tuesday they believed 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.
The reports said blood specks found in the apartment were being tested to see if they came from the missing four-year-old.
"We're not naive, but on numerous occasions the Portuguese police have assured us that they were looking for Madeleine alive," Gerry McCann said.
Meanwhile, Portuguese authorities have brought in two police dogs -- loaned out by British authorities -- to comb through the apartment where Madeleine went missing, Police Chief Inspector Olegario de Sousa told CNN on Tuesday.
Speaking from Lisbon, the inspector said one of the dogs specialized in tracing blood, but declined to comment on the reports that blood had been found in the room.
De Sousa said he still believed Madeleine had been kidnapped and no evidence had been discovered to prove otherwise.
Saturday will mark 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 the only suspect's home at the weekend apparently uncovered no new evidence. E-mail to a friend
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