The Danish inventor suspected of deliberately sinking a home-built submarine and killing freelance journalist and recent Columbia University graduate Kim Wall has allegedly told authorities that he dumped Wall's body overboard after she died in an accident, Danish police revealed Monday.

Wall, 30, was last seen on August 10th boarding the UC3 Nautilus submarine with Peter Madsen, a well-known Danish inventor and the subject of her latest piece. When Wall's boyfriend reported her missing the next morning, Madsen was arrested, and his submarine—described as "the worlds [sic] biggest amateur built submarine" on a crowdfunding website—was found sunk in a bay about 30 miles south of Copenhagen.

At the time, Madsen claimed that he'd dropped Wall off at a nearby island hours before the vessel sank. But he later admitted that "there was an accident on board which caused Kim Wall's death and that he consequently buried her at sea," Copenhagen police said in a statement released Monday.

On Monday evening, authorities also said that a headless body had been found off the coast of an island just south of Copenhagen. "It is clear that the police, like the media and everybody else, are speculating whether this female body is Kim Wall, but it is way too soon to tell," Copenhagen police spokesman Jens Moller said, according to the BBC. A preliminary investigation suggests that Madsen may have deliberately sunk the vessel.

The body has been sent for forensic analysis, and police said they could not offer any further information at this time. Madsen is being held on charges of involuntary manslaughter, and is cooperating, according to his attorney Betina Hald Engmark.

"My client has not confessed to anything, my client still pleads not guilty to the charges against him," she said. She did not elaborate on why Madsen provided a "different explanation"—as police put it—for the passenger's death.

Wall, a freelance journalist born in Sweden, graduated from Columbia University with a master’s degree in journalism in 2013, and previously studied at the Sorbonne University in Paris and the London School of Economics, according to the Washington Post. She’d written for the New York Times, The Guardian, The Atlantic, Harper’s, the South China Morning Post and Vice Magazine.

Friends told the New York Times that she was planning on moving to China with her boyfriend, and had just signed a lease on a studio apartment in Beijing.

"It is with a great concern that we, her family, received the news that Kim is missing after an interview with Peter Madsen in Denmark,” Wall’s family wrote in a statement to the Committee to Protect Journalists. “We sincerely hope that she will be found and that she is well."