Portuguese detectives hunting for missing Madeleine McCann are following up information from psychics and clairvoyants.

Officers believe that whoever abducted the 4-year-old girl from an Algarve holiday apartment 29 days ago may try to alert them to her whereabouts by claiming to have seen her in a dream or vision.

The Policia Judiciária has two dossiers of apparent visions and psychic sightings of Madeleine, placing her at locations across the world.

It is not known if a “vision” was the source of the information that led to Portuguese detectives asking British police to raid a home in London, where they believed that Madeleine might have been. A series of raids on homes in Britain have found no trace of Madeleine.

Hundreds of reports from people claiming to know where the girl is are being checked. Chief Inspector Olegario Sousa said that each claim was being taken seriously, as one could contain a message from the abductor. “That is one of the reasons that we cannot discard anything,” he said. “We must check them all in case it might be from the kidnapper.”

The decision to treat reports of “visions” seriously will fuel criticism of the investigation, which has failed to collect enough evidence to arrest any suspects. Mr Sousa said that some reports were specific, but others were as vague as dreams about a house with trees and a road.

“A few days ago we got one address near Lagos [about five miles from Praia da Luz] but it didn’t amount to anything.” Mr Sousa said he did not believe they had heard from the abductor: “If it was a message from the kidnapper, it will offer enough clues to help us to go to the right place.”

Debbie Seepersad, from Norwood, South London, was collecting her daughter from school when police arrived last Wednesday. “They said that because no one answered the door when they knocked, they were told to gain entrance to the house,” Ms Seepersad said. “I can understand why they did it. If it were my daughter, I’d want them to knock on everyone’s door.”

Leicestershire police, which is coordinating the investigation in Britain, said that a number of properties had been searched at the request of the Portuguese authorities.

Kate and Gerry McCann, Madeleine’s parents, are to appeal to the Spanish public for help in finding their daughter as the police investigations into her disappearance appear to have stalled.

They will attend meetings in Madrid today. They want to raise the issue of child abduction in general as well as appeal for information about Madeleine. They hope to meet Alfredo Pérez Rubalcaba, the Spanish Interior Minister.

The couple will also appear on a television show, which will also feature the case of Yeremi Vargas, who disappeared in the Canary Islands two months ago.

Mr and Mrs McCann, both 38, will leave their 2-year-old twins, Sean and Amelie, in the Algarve with Mr McCann’s sister and her husband. They plan to visit Berlin, Amsterdam and Morocco over the next week.