COVID-positive Vic protester in hospital.
Demonstrators who attended the third day of recurring Melbourne protests have been encouraged to get tested as a protester battles COVID-19 in hospital.
Victoria's health department has confirmed a person is being treated in hospital after attending Wednesday's at-times violent rally.
"Public health investigations are underway," a spokesman said in a statement on Thursday afternoon.
"We are urging protesters to get tested should they experience COVID-like symptoms, no matter how mild."
The infection will be included in Friday's official case tally.
The COVID-positive protester was among a mob of 400 to 600 who swarmed the Victorian capital on Wednesday, despite stay-at-home orders and repeated warnings from authorities. There are fears this could now spark a super-spreader event.
Riot squad members fired tear gas and other non-lethal rounds when rioters became increasingly hostile and refused to leave, with two officers injured and 215 arrests.
The demonstrations initially began in opposition to mandatory COVID-19 vaccinations for the construction sector and the closure of building site tea rooms, but have since turned into wider unrest.
A fourth day of the planned protests was a non-event, with demonstrators largely a no-show on Thursday despite flagging potential meeting sites.
Police pounced on protesters before they were able to gather in significant numbers, making 92 arrests.
Meanwhile, stranded Victorians fully vaccinated against COVID-19 will soon be allowed to return home from Greater Sydney.