COPENHAGEN, Denmark -- Fifteen stabs wounds were found on the headless and dismembered torso of a Swedish journalist last seen with a Danish inventor in his home-made submarine, a prosecutor said Tuesday. Police also found videos on the man's computer showing women being tortured and murdered.

Prosecutor Jakob Buch-Jepsen said at a pre-trial hearing that the cause of death for 30-year-old Kim Wall has not yet been established.

Inventor Peter Madsen, 46, is being held on preliminary charges of manslaughter and indecent handling of a corpse. Madsen says Wall died after being accidentally hit by a 155-pound hatch in the submarine's tower and he buried her at sea.

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Buch-Jepsen said the videos found on Madsen's personal computer are considered real.

Wall's torso was found off Copenhagen Aug. 21, 10 days after Madsen's arrest. The two -- who didn't know each other beforehand -- had gone out on Madsen's 40-ton submarine UC3 Nautilus on Aug. 10

The Submarine UC3 Nautilus is lifted onto a block truck from the salvage ship Vina with the help of a container crane in Copenhagen's Harbor, on August 12, 2017. Getty

Buch-Jepsen said Madsen, 46, had killed Wall at an unknown time between Aug. 10 and 11, had cut up the body and attached a belt with a pipe to the torso with the purpose of making it sink.

The missing body parts were cut off after Wall's death, Buch-Jepsen said, quoting an autopsy report.

The hearing at Copenhagen City Court was not aimed at determining the guilt of Madsen, but extending his detention to Oct. 31 while police continue to investigate.