A human skull padlocked to an exercise dumbbell has been fished out of a New Orleans waterway, leaving police with a mystery on their hands.

The skull was found earlier this month by a man using a red rope and a magnet the size of a hockey puck on a bridge to pull things out of the water below, police said in a report.

The report was recently released and obtained by The Times-Picayune/The New Orleans Advocate. The fisherman also found a handgun and a gun barrel in the water on May 18, police said.

The 6.8kg dumbbell was padlocked around the skull, which was “fully decomposed, lacking a jaw or the top row of teeth,” according to the report.

The magnet fisherman flagged down a passing police officer after making the find off the Bayou St. John Bridge.

New Orleans police did not have any further updates on the case this week, and the coroner did not say whether he had confirmed the victim’s identity, the newspaper reported.

Police have been seeking tips from the public as they investigate the case.