GERMAN police, prosecutors and forensics experts are facing a mystery after a 10-year-old boy found a human mummy in a sarcophagus in a corner of his grandparents' attic.

A CT scan has revealed a well-preserved human skull, with an arrow sticking out of the left eye socket, and large parts of a skeleton with the arms crossed over the chest, the local newspaper Kreiszeitung has reported.

Adding to the riddle is a death mask also found in the box, and the fact that X-rays show a metal layer covering the bones of the 1.49-metre-long human remains of unknown gender.

The boy's father, Lutz-Wolfgang Kettler, said his own father, who died 12 years ago, had in the 1950s travelled to North Africa and may have brought back the mummy as a grisly souvenir.

But here's where it gets strange.

The bandages used for the mummy -- which has not been unwrapped for fear of damaging the remains -- date from the 20th century and are machine-woven, said Kettler, a dentist who attended the CT scan.

Pathologist Andreas Nerlich of Munich's Bogenhausen hospital told news website Spiegel Online that, while the skull and the bones are real, the mummy is "a fake, made from one or several human bodies."

"What we have are questions upon questions" since the boy, Alexander, found the mummy about a month ago, said Kettler.

Police and prosecutors have taken note of the case in the town of Diepholz, Lower Saxony state, and are waiting for more information on where the body came from before looking into the possibility of modern-age foul play.

"We'll wait until we know how old the bones are," police spokesman Frank Bavendiek told German news agency DPA. "If they are a few hundred years old, then it's a mummy and we won't investigate."