Denmark submarine inventor says he dumped journalist's body in sea after she died in 'accident'

Peter Madsen is seen here in Dragoer Harbour, south of Copenhagen, after being rescued on August 11, 2017. Bax Lindhardt / Scanpix Denmark / AFP

The Danish inventor of a do-it-yourself submarine now says a Swedish journalist missing since August 11 died in an accident onboard the vessel and that he dumped her body in the sea, Danish police said on Monday.

The inventor, Peter Madsen, had been claiming he last saw Kim Wall when he dropped her off on the tip of an island in the Danish capital, Copenhagen, late on August 10.

Danish authorities have been searching for Wall, a 30-year-old reporter who had been writing a feature story about Mr Madsen, since she failed to return from an interview with him aboard the 18-metre Nautilus.

But Mr Madsen, who has been accused of negligent manslaughter, "told police and the court that there was an accident on board the sub that led to the death of Kim Wall, and that he subsequently buried her at sea in an undefined location of the Koge Bay", south of Copenhagen, police said.

Madsen, an entrepreneur, artist, submarine builder and aerospace engineer, went before a judge on Saturday for preliminary questioning. The case is not open to the public for the sake of further investigation, the police have said.

Read more: Mystery deepens as Danish police find sunken sub empty

Danish and Swedish maritime authorities are using divers, sonar and helicopters in the continued search for the body in Koge Bay and in the Oresund Strait between the two countries.

Several people reported seeing Wall aboard the Nautilus with Mr Madsen in waters off Copenhagen on the evening of August 10.

Photos of the two emerged online standing next to each other in the sub's tower. Wearing an orange fleece and with her auburn hair tied in a topknot, she appeared to be smiling.

When Wall failed to return home, the sub was also reported missing. Rescue crews located it around midday on August 11 in Koge Bay, about 50 kilometres south of the Danish capital.

Just after it was found, Mr Madsen was rescued, alone, and the submarine suddenly sank.

Police have since said they believe Mr Madsen sank the sub. It was brought to the surface and searched, and found to be empty.

Danish broadcaster TV2 showed Mr Madsen being interrogated by police after his rescue.

When a journalist asked him what contact information he had about the missing journalist, he responded: "Only that her name is Kim."

"I don't check the background when a journalist calls and asks 'Can I interview you'," Mr Madsen said indifferently as he entered a police car.

Wall was a freelance journalist who had reported for The Guardian and The New York Times. A graduate of the Columbia Graduate School of Journalism, she was based in New York and China.

The Nautilus was the biggest private submarine ever made when Mr Madsen built it in 2008 with help from a group of volunteers, described on a website about the vessel as "submarine enthusiasts".