Canberra, Aug 1 : South Australian state authorities are investigating a mass bird mortality event after more than 80 dead and sick greater crested terns were found on an island off the state's southeast coast.

Testing is underway to determine whether the birds were infected with the H5 strain of avian influenza, the Australian Broadcasting Corporation (ABC) reported on Saturday.

State aerial surveillance on Friday detected 49 dead and 35 sick greater crested terns on Baudin Rocks, about five km south of Cape Jaffa, the ABC reported.

The state's Chief Veterinary Officer Skye Fruean said it was "very unlikely" the birds would test negative for H5, although laboratory results were still pending.

The state of South Australia has now recorded 39 of Australia's 53 confirmed H5 bird flu cases, according to official updates, Xinhua news agency reported. Australian Chief Veterinary Officer Beth Cookson said the risk to agriculture and humans remained low.

On Friday, an expert had warned that a growing outbreak of H5N1 avian influenza in South Australia will "almost certainly" spread to an endangered species of sea lion.

Authorities in SA reported that Australia's first suspected case of the highly pathogenic strain in a seagull has been detected on the state's southeast coast.

One of the Kangaroo Island cases was detected at Seal Bay, which is home to about five per cent of the global population of the endangered Australian sea lion.

Wayne Boardman, a wildlife veterinarian from the University of Adelaide, told the Australian Broadcasting Corporation on Friday that historical events in South America have shown that sea lions and fur seals are particularly susceptible to the strain.

"The issue now with bird flu being found on Seal Bay is that it's almost certainly going to go from the birds into the sea lions," he said.

The H5N1 strain killed an estimated 30,000 sea lions in South America within six months in 2022 and killed an estimated 13,359 southern elephant seal pups on Australia's Heard Island in the Southern Ocean between August 2025 and January 2026.

The SA government on Wednesday announced that beach tours on Seal Bay would be temporarily suspended to protect local sea lion and seal populations.

Minister for Agriculture, Fisheries and Forestry Julie Collins told reporters on Friday that the government would continue working with experts to contain the spread of the strain. She said there has been no evidence of the virus in agricultural or poultry systems and the threat to human health remains low.

/IANS