There were no traces of exhaust gases found on Danish inventor Peter Madsen’s submarine — casting doubt on his explanation for the death of a Swedish journalist, according to testimony Tuesday.

Madsen claims freelancer Kim Wall died last August when toxic fumes filled his UC3 Nautilus while he was on deck.

But a submarine expert testified that an investigation proved otherwise.

“We have not been able to detect CO2 in the submarine,” Ditte Dyreborg, a lieutenant commander in the Danish navy, told the court, according to Danish broadcaster DR. “And the experience from military submarines is that it wouldn’t pose a significant risk.”

Madsen, 47, has admitted chopping up Wall’s body and tossing the parts into the sea — but has insisted her death was accidental. He invited the 30-year-old writer onboard for an interview.

Prosecutors said Madsen tortured Wall with a saw and sharpened screwdriver before killing her to satisfy violent sexual fantasies.

Dyreborg is among the final witnesses who will be called in Madsen’s case.

A verdict is expected April 25.

With Post wires