Updated

The sinking of an amateur submarine was a “deliberate act,” Danish investigators said, as officials on Monday continued searching for the body of a Swedish journalist believed to have been aboard the doomed craft.

Peter Madsen, 46, was the lone survivor after his 40-ton homemade Nautilus sub foundered off Denmark’s eastern coast on Thursday evening. Madsen was arrested hours after he was rescued, hit with preliminary manslaughter charges in the death of 30-year-old Kim Wall, who was seen departing on the sub with Madsen shortly before the Nautilus sank.

Madsen initially told authorities he dropped off Wall prior to the sub’s sinking, but police say Madsen has since changed his statement, though they haven’t elaborated on how, the BBC reported.

Officials now believe Wall, who was based in Brooklyn, N.Y., was aboard the Nautilus when it sank. But though the craft has been raised, Wall’s body was not found inside of it.

“It appears to be a deliberate act to sink the submarine,” Jens Moller, the chief homicide investigator of the Copenhagen police, said at a Sunday news conference.

Authorities have not said what that act was or what the motivation behind it may have been.

Madsen has maintained his innocence and told a local television station the sub sank due to technical issues.

“I was toying with various things on the submarine and then an error occurred,” he told TV2.

What is likely the last picture taken of Wall, showed the freelance journalist, smiling, aboard the sub and standing alongside Madsen, whose back is turned, just before the Nautilus departed on its ill-fated Thursday voyage.

Wall had been writing about Madsen and the Nautilus at the time of the incident. And though investigators charged Madsen with preliminary manslaughter, they sent mixed signals about whether they had come to a firm conclusion about Wall’s fate.

“We’re still hoping that we’ll find Kim Wall alive,” Moller said. “But we are preparing ourselves for the fact that she may not be.”