Scores of sightings of the child in Europe, the United States and Hong Kong were passed along by independent witnesses and international police forces but weren't followed up by investigators, The Daily Telegraph reported.
Madeleine was 3 when she disappeared from her family's apartment in the Portuguese resort town of Praia da Luz in May 2007.
Her parents, Kate and Gerry McCann, discovered the Portuguese police file last month during court proceedings against Goncalo Amaral, the detective who tried to publish a book accusing the couple of covering up their daughter's death, the British newspaper said.
Portuguese officials released the file Tuesday after The Daily Telegraph filed a request, the newspaper said. The document included several sightings of the girl in Europe and elsewhere, along with remarks by investigators that some the information wasn't relevant to the investigation.
"There are instances where information which we think is very credible and worthy of information has not been actioned," Kate McCann said. "We're gutted. It's absolutely shocking and difficult. Some of the information handed in was very credible. It's heartbreaking to know that it seems to end there."
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