By Jacob Gronholt-Pedersen

COPENHAGEN (Reuters) - Danish police said on Saturday they were preparing to search a sunken submarine owned by Danish inventor Peter Madsen who has been charged with the inadvertent manslaughter of a journalist.

The police said that Madsen, 46, was being held in custody for 24 days, accused of killing Swedish woman Kim Wall, 30, who they said had been on his submarine before it sank on Friday.

Madsen was rescued on Friday morning in a navy operation and taken ashore after his homemade 17-metre submarine went down.

The vessel was recovered on Saturday in Koge Bay, south of Copenhagen, at a depth of seven meters, and taken into harbor.

It will be partly drained of water and searched by the police late on Saturday and early Sunday.

Madsen, an entrepreneur known as an artist, submarine builder and aerospace engineer, went before a judge on Saturday behind closed doors for preliminary questioning. His defense lawyer, Betina Hald Engmark, told Reuters he denied the charges.

The police said on Friday the inventor had said he had dropped Wall off in Copenhagen on Thursday night.

The police in Sweden said they had tried without success to contact her by phone and that her family had not heard from her.

The submarine, UC3 Nautilus, is one of three constructed by Madsen. It can carry eight people.

(Reporting by Jacob Gronholt-Pedersen, additional reporting by Stine Jacobsen in Copenhagen and Anna Ringstrom in Stockholm; Editing by Andrew Bolton)