A cancer cluster among workers in a suburban Sydney office appears to have occurred by chance after extensive radiation testing.
Teams of nuclear radiation experts were brought into Liverpool City Council's offices in July and August after five current and past workers came forward with thyroid cancer.
Surveys of radiofrequency electromagnetic energy and office hygiene were also conducted.
Ionising radiation is a major known risk factor for thyroid cancer.
But in a final report the council, in Sydney's southwest, said no identifiable health hazard was found in the two relevant levels of its Moore Street building.
"The apparent cancer cluster, although unusual, would appear to have occurred by chance," the report concludes.
"Council thanks all those who were involved in this matter. Specifically, we thank those who had been diagnosed with cancer for their co-operation and wish them well for their future health."
Staff are expected to be briefed by the experts on Thursday ahead of a planned reopening of the office floors.
"I hope this information provides some peace of mind not only to those still working in the building but also to those who are still facing medical challenges," the council's acting chief executive Jason Breton said on Tuesday.
The five cases were all diagnosed between four months and five years ago.
All but one was aged under 50 at the time of diagnosis, with three of the cases in women and two in men.
No clear risks for thyroid cancer were identified for any of these individuals through the interview process.
A sixth person reported a thyroid condition but did not consent to take part in a NSW Health department investigation and was excluded.
About 4000 Australians are diagnosed with thyroid cancer each year, making it the nation's ninth-most commonly diagnosed.
The findings come a day after the same council, one of the largest in NSW, lost a court bid to stop administrators taking over following claims of widespread dysfunction.
A damning interim report found problems with Liverpool City Council's recruitment processes, procurement irregularities and allegations of a toxic work environment.
The council can appeal the court's decision.
