A Danish inventor who built a submarine has been arrested over the disappearance of a journalist - who prosecutors believe was on the ship before it sank.
Peter Madsen is being held on manslaughter charges after Swedish journalist Kim Wall vanished shortly after his 40-tonne amateur submarine sank off Denmark's coast on Friday.
Ms Wall, a 30-year-old Swede who had worked for the New York Times, The Guardian, South China Morning Post and Vice Magazine, boarded the sub on Thursday evening.
Madsen has denied responsibility for the fate of Ms Wall, claiming she disembarked before the vessel went down.
The journalist's boyfriend alerted authorities on Friday morning that the sub, named the UC3 Nautilus, had not returned to Copenhagen as expected.
A major search was launched involving the Danish Navy, including two helicopters and three ships, which briefly spotted the sub before it sank.
Ms Wall had been with Madsen as they sailed inside the submarine on Thursday, with Madsen claiming he then dropped off his passenger at Copenhagen harbour during the night.
Rescue crews reported seeing Madsen standing aboard the submarine wearing trademark military fatigues in the vessel's tower whilst it was still afloat.
The wreck has since been salvaged but no body found.
Despite his protestations, Madsen has now been detained on preliminary manslaughter charges.
Ms Wall, who lived in the US and China, studied at the Sorbonne university in Paris, the London School of Economics and at Columbia University in New York.
A family statement said: "It is with great dismay that we received the news that Kim went missing during an assignment in Denmark."
Madsen is due to appear in court at a later date.