HELSINKI -- Danish police say the owner of a home-built submarine has told investigators that a missing female Swedish journalist died onboard in an accident, and he buried her at sea in an unspecified location.

Copenhagen police said Monday that submarine owner Peter Madsen will continue to be held on preliminary manslaughter charges. Police declined to provide more details.

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

Kim Wall, a 30-year-old journalist reported to be aboard Madsen's submarine UC3 Nautilus on an assignment, disappeared more than a week ago. Madsen has denied any wrongdoing, and initially denied any role in her disappearance. The sub sank Aug. 11.

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Madsen previously said he last saw Wall when he dropped her off on an island off Copenhagen on August 10 after she conducted an interview with him on the submarine.

Police said Monday that Madsen "told police and the court that there was an accident onboard the sub that led to the death of Kim Wall, and that he subsequently buried her at sea in an undefined location of the Køge Bay," according to The Guardian of Britain.

"We believe he is telling the truth when he says she died in the submarine," The Guardian quoted Danish police chief Steen Hansen as telling Swedish news agency TT. Hansen apparently didn't indicate whether investigators believe the inventor's account of an "accident" killing Wall.

Wall's family previously told The Associated Press that Kim worked in many dangerous places as a journalist, but it was unimaginable that "something could happen ... just a few miles from the childhood home."