More than 500 tennis players and officials were ordered into isolation in the Australian city of Melbourne on Thursday as authorities reintroduced coronavirus restrictions after a worker at a quarantine hotel tested positive for the virus.
The city reimposed an order for masks indoors and a limit on gatherings of 15 people after the state's run of 28 days with no new local cases came to an end.
Melbourne, Australia's second-biggest city, is preparing to host the Australian Open tennis tournament from Monday but play at six warm-up events was heavily disrupted by the new infection with organisers Tennis Australia calling off all matches for Thursday.
The case of the infected Grand Hyatt worker was announced late on Wednesday and Victoria state Premier Daniel Andrews told reporters an initial round of tests had found no new cases.
The Australian Open was likely to go ahead though "there were no guarantees", he said.
"At this stage, the tennis shouldn't be impacted by this. These things can change. Every Victorian knows these are uncertain times," Andrews told a news conference.
The Grand Hyatt was one of three main quarantine hotels used by players and officials arriving in Melbourne for the Grand Slam event.
About 1,200 players, coaching staff and officials arrived in Australia in the middle of last month and went into a mandatory 14-day isolation. Most players were released from quarantine last month.
Australia has ranked among the world's most successful countries in handling the novel coronavirus, largely because of decisive lockdowns and borders sealed to all but a trickle of travellers.
Western Australia state, which is on a five-day lockdown after one positive case was detected on Sunday, has since found no new local cases. The states of New South Wales and Queensland also reported no new cases on Thursday.
In all, Australia has had 22,000 local cases and 909 deaths.
But its quarantine hotels, where all international arrivals have to spend two weeks, have proved a weak link with the new infection in Melbourne the latest case to emerge from one.
The cabinet is set to meet on Friday to consider whether the quarantine hotel programme should use facilities in more remote, regional centres given the tendency for the virus to escape from hotels into the community.
Prime Minister Scott Morrison said that hotel quarantine remained the "most effective" arrangement.
Morrison reiterated a free vaccination programme was on tack to begin later this month.
Australia has secured an additional 10 million doses of the Pfizer-BioNtech vaccine taking its total to 150 million, which will also be distributed to neighbouring Pacific Island countries, Morrison said.