The mystery began when a tracking device formerly attached to the shark in 2004 washed up on an Australian beach four months later, showing signs it had been bleached by stomach acid.
Data from the device revealed a rapid temperature rise from 46 to 78 degrees Farenheit, along with a sudden sharp 580m plunge.
Researchers say this proves the device was eaten by something much bigger, and that the temperatures recorded indicate it travelled into another animal’s digestive system.
Film maker Dave Riggs, who tagged the shark originally, said: “When I was first told about the data that came back from the tag that was on the shark I was absolutely blown away.
“What’s going to eat a shark that big? What could kill a [9-foot] great white?”
What could this mystery predator be? That’s the topic of discussion in an upcoming documentary by the Smithsonian Institute - Hunt For The Super Predator - to be aired in the US on 25 June.
One theory is the shark was possibly attacked by a larger great white, and indeed, there here have been previous incidences of great white shark cannibalism.
In 2009 a 20ft long shark took a chunk out of a smaller great white just off the Queensland coast.
Shark expert Hugh Edwards told Channel 7 News in Australia: “The cannibal thing is what great whites do. They’ll eat anything, including their own kind.”
Riggs told the Mail Online he had spoken to sperm whale hunters in the Bremer Bay area who reported sightings of an animal about 10-and-a-half metres long and others that were tracked travelling at up to 4.5knots but did not surface.
But he feels it is more likely the shark was eaten by another large shark of the mackerel species, though he added: "But by the same token I'm not 100 per cent convinced."
Riggs says based on the tag data the animal that swallowed the device had a stomach area at least 1m wide.
"The notion of gigantism is well documented in species, to me that plausible," he said.
"This is nature at work and we are just trying to get to the bottom of something that happened years ago."