Journalist Kim Wall, who vanished on August 10th, when she left the port of Copenhagen on the UC3 Nautilus, a submarine built and operated by Peter Madsen.
"He's relieved right now that the information has been brought to the public", she said.
"We believe he is telling the truth when he says she died in the submarine", a Copenhagen police official said, according to Business Insider. He denied any knowledge of her disappearance. Divers and sonar detection systems are being deployed around the waters of Køge Bay and Öresund.
Mr Madsen initially said he dropped Ms Wall off after dark on 10 August, close to where they had met earlier.
"Copenhagen Police may additionally disclose that the preliminary charge of manslaughter is upheld".
Madsen, 46, was rescued and later charged with negligent manslaughter after Wall was not found aboard the sub. She appeared to be smiling. Her boyfriend reported her missing on Friday morning.
The entrepreneur was rescued after the submarine sank and then arrested on dry land after claiming it was an accident.
Wall, a graduate of Columbia University and London School of Economics, was based between Beijing and NY.
Wall was a freelance journalist who had reported for The Guardian and The New York Times.
She had been researching a feature about Mr Madsen and his 40-tonne submarine, which at one stage was the largest privately-made vessel of its kind.
The volunteers were engaged in a dispute over the Nautilus between 2014 and 2015 before members of the board chose to transfer the vessel's ownership to Madsen, according to the website.