COPENHAGEN, Denmark (AP) — A judge will decide Saturday if the owner of an amateur-built submarine should be held in custody during an investigation into whether he is responsible for the disappearance of a Swedish woman who had been onboard his submarine that sank off Denmark's east coast.

Peter Madsen was arrested Friday on preliminary manslaughter charges after his 40-ton, nearly 18-meter-long (60-foot-long) UC3 Nautilus sank. He has denied responsibility for the fate of 30-year-old Kim Wall, saying she had disembarked earlier.

The woman's boyfriend alerted authorities that the sub had not returned, prompting a major search involving two helicopters, three ships and several private boats. The Navy said that the sub had been spotted sailing but then sank shortly afterward.

Kristian Isbak, who had responded to the Navy's call to help locate the ship, sailed out immediately Friday and saw 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 told The Associated Press. "(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 the woman off on an island in Copenhagen's harbor a few hours into their Thursday night trip.

Danish media said the Sweden-born freelance journalist attended Columbia University in New York and had also lived in Beijing. She has written for the New York Times, The Guardian, the South China Morning Post and Vice Magazine, among others.

A salvage vessel, the Vina, was Saturday working on raising the submarine, which was seven meters (23 feet) under water off Copenhagen's south island of Dragoer.

In theory, the vessel can dive up to 470 meters (1,550 feet) but has rarely gone deeper than 40 meters (132 feet), according to its Web site.

The hearing starts at 1200 GMT. If tried and found guilty, Madsen would face between five years and life in prison.