By Duncan Murray and Melissa Meehan in Sydney

The deadly H5N1 bird flu may have been detected in a migratory bird in Australia’s most populous state, which was previously free of the virus.

Five cases of the deadly avian influenza have been confirmed so far in seabirds in two states in Australia over the past week.

But a snap press conference called on Friday by NSW Agriculture Minister Tara Moriarty and the state’s chief veterinary officer Jo Coombe confirmed the virus may have reached a third state.

Samples from a Giant Petrel near Hawks Nest, a town about 228km north of Sydney, has tested positive for H5 influenza in preliminary testing at the department’s laboratory at the Elizabeth Macarthur Agricultural Institute.

“This latest development is incredibly concerning for both agriculture and for wildlife,” Ms Moriarty told reporters.

“But NSW and the rest of the country have been preparing for this moment for many years.”

Chief veterinary officer Jo Coombe said crews would increase surveillance to detect any further cases.

“The State Coordination Centre has been stood up in Orange, we have established the H5 bird flu call centre and we are briefing all key stakeholders on the current situation,” Dr Coombe said.

“We are using the best available data now to target actions for our most at-risk wildlife species and important natural places.”

Until June, Australia had been the only continent free of the highly contagious virus, which has wiped out millions of birds worldwide and also killed mammals.

Five birds have returned positive results for the strain since it was first detected on the Australian mainland on June 14.

They were a brown skua found in Esperance, WA, on June 14, a giant petrel on South Australia’s Fleurieu Peninsula on June 14, a giant petrel in Esperance on June 18 and a giant petrel found at Roses-Quallup Beach at Esperance confirmed on Tuesday.

All positive cases have occurred in wild birds, with no signs the virus has spread to local poultry populations.

There has also been no evidence of mass mortalities in wildlife.

A temporary ban on poultry products from Australia imposed by Papua New Guinea’s National Agriculture and Quarantine Inspection Authority was lifted on June 24.

People are being urged to avoid contact with sick or dead wildlife and report any finds to an emergency hotline and record locations and take photos.

News all day, every day at CityNewsQBN.com.au.