Madrid - Spanish private detectives investigating the 2007 disappearance of a British girl from a resort in Portugal uncovered an Internet paedophile ring, El Mundo reported in its online edition on Monday.
Police arrested 13 suspects as a result of the investigation by officials from the Barcelona-based Metodo-3 agency, which had been hired by Gerry and Kate McCann to trace their daughter Madeleine, said the report.
Madeleine McCann disappeared on May 3, 2007, from their holiday apartment at the Portuguese resort of Praia da Luz as they dined with friends at a nearby restaurant. She was three years old at the time.
The agency's investigators were hired six months after her disappearance.
Two months into their investigation, they received an email claiming that Madeleine featured in a paedophile video posted on the Internet, El Mundo reported.
Although it turned out that she did not feature in the video, the agency tipped off Spanish police who subsequently arrested the suspects in a series of raids in December 2008.
As well as those arrested, police questioned another 10 people and seized a large quantity of computer equipment.
Approached by reporters, Metodo-3 was unable to confirm the report.
Spain has staged a series of operations against Internet child pornography in recent years, arresting more than 1 200 people over the last five years - of whom 408 were arrested in 2008 alone.
Madeleine McCann's parents have been funding a private investigation to try to find out what happened to their daughter.
The Portuguese authorities closed their probe into her disappearance in July 2008. - Sapa-AFP