Concerns are mounting after three people were hospitalised after contracting COVID-19 at a country music gig in western Victoria.
The live music performance was held at the Hamilton Golf Club on November 14 for vaccinated patrons only.
It was the first event the Hamilton Country Music Club has hosted in the wake of the pandemic, and a number of health precautions were put in place.
All patrons had their vaccination status checked upon entry, according to the event organiser, and numbers were strictly limited.
However, the event has since been listed as a high-risk venue by Western District Health Services (WDHS) after 18 people who attended the performance contracted COVID-19 .
Of those 18, three people have been admitted to the University Hospital Geelong in a stable condition.
The confirmed cases are between nine and 86 years old.
Nursing home linked to positive case
The local hospital has initiated its coronavirus response and a mass testing clinic has been set up at the Hamilton Showgrounds, where it was expected to remain for the rest of the week.
Concerns have been raised after an individual that contracted the virus subsequently volunteered at The Birches aged care facility in Hamilton.
That facility has enacted its COVID-safe protocols, and no cases have been detected at the centre yet.
It was understood several local disability services have also been impacted by the cluster.
WDHS chief executive, Rohan Fitzgerald, said the health service has restricted visitor access at its aged care facilities and cancelled all category 2 and 3 surgeries scheduled this week.
It was not yet known how the coronavirus cluster started.
The ABC contacted the event organiser, who declined an interview, but confirmed the vaccination status of all patrons was checked and believed that all patrons were fully vaccinated.
"Over 300 people presented for testing at the mass testing clinic at the Hamilton Showgrounds today, taking the total tested since Friday to 476," Mr Fitzgerald said.
Additional testing capability is being sent to the hospital from Wednesday morning, including a rapid PCR testing unit capable of processing 16 tests per hour.
The Caledonian Hotel in Hamilton is the only Tier 1 site listed by Western District Health Services thus far.
WDHS has urged anyone who attended that venue on November 18 to get tested as soon as possible.
