The identity of a mystery "forest man" who has been living in an abandoned house in woodland in Germany's Rhineland remains unclear, although he appears to be a US citizen, German police said Wednesday. The man, reported to be aged 42, is being held as police found 150 grams of marijuana in the house near Kobern-Gondorf in the state of Rhineland-Palatinate, dpa reported. Police found the man, who speaks German with an American accent, after following up on a tip from a walker. Although the forest man - as he has been dubbed by the local media - told police he had been living in a tent, subsequent investigation revealed an improvised room of around two metres by two metres on the roof of the dilapidated house. According to police, the man was in possession of an old US sailing certificate, although police could not positively identify the man by its photograph. The man's father has reported him missing in the US.