British experts have flown to the Algarve to re-examine the scene of Madeleine McCann's abduction, Portuguese police said.
They said four British "specialists" who are not police officers had arrived in the country on Thursday.
It is understood their arrival follows requests from the McCann family through British police in the Algarve.
The men were seen measuring the window to the McCann's apartment, pacing out measurements around the building and even walking as far as the home of Robert Murat, the only official suspect or "arguido" in the case, according to reports.
They were also reportedly seen holding a map of the Mark Warner holiday complex in Praia da Luz where the abduction took place just over three weeks ago. It was unclear whether the experts were scenes of crime officers.
Leicestershire Police said it was unaware of any of its own scenes of crime officers being sent to the Algarve and the Association of Chief Police Officers declined to comment specifically.
Chief Inspector Olegario Sousa of the Policia Judiciaria (PJ) said the specialists had come to the Algarve in "collaboration" with British police.
The move follows intense criticism of the Portuguese handling of the case. Earlier this week one child protection expert who visited Praia da Luz shortly after the abduction described the area around the McCanns' holiday apartment as the "worst preserved" crime scene he had ever seen.
It is understood that the move follows a request from the McCann family for more direct examinations of the scene in case something was missed.
Madeleine, four, was abducted as she slept in her parents' holiday apartment on the night of May 3 while the couple were eating dinner nearby. The latest development comes as Gerry and Kate McCann finalise plans for a series of trips across Europe to raise Madeleine's profile.
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