Victoria Police said emergency services were responding to reports of a collapse at Ballarat Gold Mine in Mount Clear about 4.50pm on Wednesday.
A spokesperson said the situation was developing and further information would be provided when available.
Ambulance Victoria said paramedics were at the scene and an air ambulance has been dispatched.
The mine's website states it operates deep beneath buildings, streets and homes and has an extensive network of tunnels.
Worksafe inspectors and a technical specialist are also responding.
In a statement, Victorian Premier Jacinta Allan said she was thinking of every worker and family impacted by the collapse.
"Tonight will be a long night for them and for the entire Ballarat community," she said.
Ballarat Gold Mine declined to comment.
It is owned by Victory Minerals and the mine is not open to the public.
In 2007, 27 miners were trapped 300 meters underground at Ballarat Gold Mine for several hours.
The men were not hurt and were eventually winched to safety by a crane.
The Mount Clear area has been the focus of the search for Ballarat mother Samantha Murphy, however, there is nothing to suggest any link.
Patrick Orren Stephenson has been charged with murdering the mother of three at Mount Clear and her body has not yet been found.
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