Madeleine McCann police are searching for a second German drifter who lived in the Algarve at the time she vanished.
The man is believed to be a former friend of rapist Christian Brueckner, suspected of abducting and murdering the three-year-old in 2007.
Officers are understood to be treating him as a witness, not a suspect.
It is thought he lived in a camper van near a remote reservoir nine miles from Praia da Luz.
At least one old associate of Brueckner, 43, has been quizzed about the mystery by German police in Portugal.
A source said: “They didn’t seem to know his name. They said he may have stayed up at Barragem da Bravura. My friends and I don’t recall Christian hanging out there but he was pretty private.”
Notes left at the resort in Praia da Luz a year later and sent to a Dutch newspaper are said to identify the vast area of water as Maddie’s “final resting place”.
Brit Kit Thackeray has lived next to the reservoir for more than 30 years. He said: “There were Germans living in campers all around here in the early 2000s. He could be anywhere now.”
The area was searched days after Maddie vanished but local news reports said police spent only two hours there and did not send divers into the water.
