``Steve was hit by a stingray in the chest," said local diving operator Steve Edmondson, whose Poseidon boats were out on the Great Barrier Reef when the accident occurred.
``He probably died from a cardiac arrest from the injury," he told Reuters news service.
Police and ambulance officials later confirmed Irwin had died and said his family had been advised.
The Australian Broadcasting Corp. said Irwin was diving near Low Isles near the resort town of Port Douglas, about 1,260 miles north of Brisbane.
A helicopter carrying paramedics flew to the island.
Staff at Australia Zoo, Irwin's zoo in southern Queensland, said they had heard the reports but could not comment.
Irwin is famous for his enthusiasm for wildlife and his catch cry ``Crikey!" in his television program ``Crocodile Hunter," which was first broadcast in Australia in 1992 and has been aired around the world on the Discovery channel.
He rode his image into a feature film and developed the Australia Zoo as a tourist attraction.
Irwin had received some negative publicity in recent years. In January 2004, he stunned onlookers at his zoo's reptile park by carrying his 1-year-old son into a crocodile pen during a wildlife show. He tucked the child under one arm while tossing the 13-foot reptile a piece of meat.
Authorities declined to charge Irwin for violating safety regulations.
Irwin was also seen as a vocal critic of wildlife hunts in Australia. The federal government recently dropped plans to allow crocodile safaris for wealthy tourists in the Northern Territory following his vehement objections.
Irwin's wife, Terri, is also a wildlife specialist and she shared credits with him on the TV show. Terri Irwin, who was born in Oregon, was believed to be hiking in Tasmania. The Irwins have two children.
