Copenhagen (CNN) Peter Madsen, the Danish inventor suspected of killing Swedish journalist Kim Wall, has denied that he was responsible for her murder, Copenhagen police said Friday.

Madsen is in custody and being questioned by investigators. Prosecutors said Thursday that they intend to file formal charges against Madsen for murder as well as "indecent interference with a human corpse."

Peter Madsen claims Kim Wall died in an accident.

Wall, 30, disappeared after boarding Madsen's homemade submarine on August 10 for a story. She was last seen on that day in an image that allegedly showed her standing with Madsen in the tower of the submarine in Copenhagen Harbor.

On Wednesday, Danish police confirmed that the DNA from a headless torso found washed up on an island near Copenhagen matched that of Wall. Blood found on the submarine was also a match for Wall, according to chief investigator Jens Møller Jensen.

This image is thought to be the final photo of Swedish journalist Kim Wall. She's seen standing with Peter Madsen in the tower of his private submarine on August 10, 2017 in Copenhagen Harbor.

Møller Jensen said the body had apparently been punctured to let the air out before sinking it, and it was weighted down in a presumed attempt to prevent it floating.

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