A third case of H5 bird flu has been confirmed in Western Australia after five giant petrels were found on a beach near Esperance on the state’s southern coastline.

It is the fourth confirmed case of avian influenza in Australia, with three confirmed in WA and one in South Australia.

WA’s Agriculture Minister Jackie Jarvis told media a member of the public reported five giant petrels at Roses Beach on Sunday.

“Only one of the petrels has returned a suspected positive result for bird flu,” she said.

“The other four birds returned negative results.”

A giant petrel found in Quindalup, in WA’s South West, was confirmed to test positive for the bird flu on Saturday.

The CSIRO tested samples from the suspected cases to determine if they are positive.

“Results of a further suspect positive detection in a giant petrel on the WA south coast at Roses Beach, 30kms west of Esperance, are pending,” a statement from the Department of Primary Industries and Regional Development read.

Ms Jarvis said there were still no signs of mass mortalities, or detections in poultry or wildlife.

“There is no evidence of disease transmission here on the Australian mainland,” she said.

South Australia confirmed its first case of avian influenza on Wednesday, with one bird testing positive.

The migratory seabird, a giant petrel, was found at Knights Beach on the Fleurieu Peninsula on June 14 next to another petrel, which tested negative.

WA has two confirmed cases of H5 bird flu that were found in Esperance last week.

A sick brown skua was found on a beach and taken to a wildlife hospital on June 14, another giant petrel was found four days later.