By JAN M. OLSEN, Associated Press

COPENHAGEN, Denmark (AP) — A Danish court ordered the owner of an amateur-built submarine Saturday held in pre-trial detention for 24 days while police investigate the disappearance of a Swedish journalist who had been on the ship before it sank.

Peter Madsen was arrested Friday on preliminary manslaughter charges, hours after his 40-ton, nearly 18-meter-long (60-foot-long) submarine sank off Denmark’s eastern coast.

The inventor, who is from Denmark, has denied responsibility for the fate of 30-year-old Kim Wall, saying the journalist disembarked before his vessel went down.

Judge Kari Soerensen announced the ruling after a two-hour custody hearing held behind closed doors.

Madsen’s defense lawyer, Bettina Hald Engmark, said her client maintains his innocence. He is “willing to cooperate” and hasn’t decided whether to appeal the detention ruling, Hald Engmark said.

Before the hearing was closed, the courtroom was packed with Danish and Swedish reporters and the 46-year-old Madsen’s relatives. Madsen smiled and chatted with his lawyer.

“I would very much like to express myself,” he said after the preliminary charges were read.

Prosecutor Louise Pedersen said Madsen faces the preliminary manslaughter charge “for having killed in an unknown way and in an unknown place Kim Isabell Frerika Wall of Sweden sometime after Thursday 5 p.m.”

Wall’s boyfriend alerted authorities early Friday that the sub, , named the UC3 Nautilus, had not returned to Copenhagen as expected. The Danish Navy launched a major search involving two helicopters, three ships and several private boats. The Navy said the sub was seen sailing, but then sank shortly afterward.

Kristian Isbak, who had responded to the Navy’s call to help locate the ship on Friday, told The Associated Press he first spotted Madsen standing wearing his trademark military fatigues in the submarine’s tower while it was still afloat.

“He then climbed down inside the submarine and there was then some kind of air flow coming up and the submarine started to sink,” Isbak said. “(He) came up again and stayed in the tower until water came into it” before swimming to a nearby boat as the submarine sank, he added.

Madsen told authorities he had dropped Wall off on an island in Copenhagen’s harbor a few hours into their Thursday night trip.

“It is with great dismay that we received the news that Kim went missing during an assignment in Denmark,” her family said in statement emailed to The Associated Press.

The Sweden-born freelance journalist studied at the Sorbonne university in Paris, the London School of Economics and at Columbia University in New York, where she graduated with a master’s degree in journalism in 2013.

She lived in New York and Peking, her family said, and had written for The New York Times, The Guardian, the South China Morning Post and Vice Magazine, among other publications.

A salvage vessel on Saturday raised the submarine, which was seven meters (23 feet) under water off Copenhagen’s south island of Dragoer. The submarine was brought up some 7 kilometers (4.3 miles) off the coast and is expected to be transported to land at some point.

In theory, the Nautilus can dive up to 470 meters (1,550 feet) but has rarely gone deeper than 40 meters (132 feet), according to Madsen’s business web site.

If tried and found guilty, Madsen would face between five years and life in prison.