Danish inventor held on murder charge after home-made sub sinks and journalist disappears

The owner of an amateur-built submarine was arrested on suspicion of murder on Friday after his vessel sank off Denmark’s coast and a journalist who had joined him for what was supposed to be a short voyage was reported missing, Copenhagen police said.

In a statement on Friday night, police said the man denied killing the missing woman and reported dropping her off on a redeveloped island in Copenhagen’s harbour about three and a half hours into their Thursday night trip.

The statement did not identify the submarine’s owner, Peter Madsen, 46, but the Danish inventor’s financing of the project through crowdfunding and first launch of the UC3 Nautilus in 2008 made headlines.

The 40-tonne, nearly 18-metre-long vessel has been described as the largest privately built submarine of its kind.

Before his arrest, Madsen appeared on Danish television to discuss the submarine’s sinking and his rescue. It was the journalist’s boyfriend who alerted authorities early on Friday that the sub had not returned from a test run, police said.

“I am fine, but sad because Nautilus went down,” Madsen told Denmark’s TV2 channel, which aired footage of him getting off what appeared to be a private boat and giving a thumbs-up sign.

Madsen said “a minor problem with a ballast tank” – a compartment that holds water to provide stability – “turned into a major issue” that ultimately caused the submarine to sink.