Five people who all worked in the same Sydney council building have developed thyroid cancer, sparking fears of a potential cancer cluster.
Liverpool City Council, a local government body in Sydney's southwest, confirmed five current or former staff working at its Moore Street office building developed cancer in the last three to five years.
They all worked on levels five and six of the office building.
A sixth person had reported a thyroid condition but opted out of investigations.
In a statement provided to Australian media the council said it was taking the matter "very seriously" and had engaged an independent environmental health consultant.
The New South Wales Department of Health is also investigating.
Workers on the building's sixth floor have been relocated while the investigations take place.
"The decision to relocate staff is in response to the council's high level of concern for the welfare of its staff," the council said.
"Our thoughts are with those affected and we wish them a prompt recovery."
Jenny Havilah worked on level six and was recently diagnosed with thyroid cancer.
"I had my thyroid and some lymph nodes removed and I'll get the results in a week or so," Havilah told 9News.
She said the potential cluster "certainly sounds very sinister".
The council's acting CEO Jason Breton told staff about the cases during a meeting this week.
In audio obtained by 9News, he said three of the women were "well and working", but Havilah said she is "far from well and working".
The council told 9News the women have been told it is "unlikely there is a causal connection between our workplace and the cancer diagnosis".
New South Wales local government union the United Services Union is calling for the building to be cleared completely.
"We're concerned the issue may be more widespread so we'd be waiting for an independent medical assessment to unequivocally clear the area before we would be recommending our members return," acting general secretary Daniel Papps told 7NEWS.
A cancer cluster is when an unusually high number of people get the same type of cancer after a common exposure.
In 2006, 10 women out of 550 at the broadcaster ABC's Brisbane office were diagnosed with invasive breast cancer - six times more than the expected rate.
The precise cause of the cases was never determined but the investigation led to the ABC closing its studios and building new headquarters.
