Up to 600 Australian Open players and staff go into isolation after a hotel worker tests positive for Covid-19

Victoria Premier Daniel Andrews said Wednesday that a 26-year-old volunteer firefighter who had been working as a resident support officer as part of the tournament tested positive for the virus.

The state had not seen local transmission of the virus in 28 days when the announcement came at about 9pm local time on Wednesday.

New restrictions have now been placed on the state's 6.7 million inhabitants. Masks are mandatory in indoor public places and new limits are in place on the number of people who can gather in a household.

Andrews said the new rules were being put in place "through an abundance of caution" and because of the possibility that the case could have been caused by a new strain of the coronavirus -- although he said the genomic sequencing needed to determine whether that was the case hasn't finished yet.

The unnamed man last worked at the Grand Hyatt hotel on January 29 and tested negative for the virus at the end of his shift that day. However, he subsequently developed symptoms and tested positive on Wednesday.

As a result, Andrews said 500-600 people staying at the hotel have been deemed "close contacts" and will have to isolate until they return a negative test.

He said that the situation should not impact the Australian Open itself, which is set to begin on Monday.

When asked by a reporter whether this was the worst-case scenario ahead of the year's first Grand Slam event, Andrews replied: "I wouldn't describe it in those terms. We've got one case. We're going to work very hard to keep numbers as low as we possibly can. Decisions have been made, and we'll proceed as we can next week."

The run up to the tournament has been shaped by coronavirus fears. Players arriving in Victoria had been placed into a 14-day quarantine ahead of their grand slam matches.

Most have been allotted five hours each day to go out and train in strict bio-secure bubbles, but 72 players have been unable to leave their hotel rooms and cannot practice, under strict quarantine rules after passengers on their flights tested positive for Covid-19.

To make up for the lost training time, tournament organizers scheduled a new warm-up event for players who have been unable to train during quarantine. However, the new case identified on Wednesday forced the organizers to cancel the matches scheduled for Thursday.