Fresh reports have revealed a slim 18-second window was all it took for Covid-19 to break through Adelaide's hotel quarantine and ultimately make its way to the Melbourne CBD.
The latest cluster is believed to have emerged from the Playford Hotel in Adelaide's CBD on May 3.
The door to the room of a man known as Case A opened for a matter of seconds, as the man in his 30s bent down to collect a meal outside.
The person next door, soon to be labelled Case B, was infected shortly after.
"On one occasion, Case B opened his room door to collect his meal, then 18 seconds later Case A opened his door to collect his meal," a report from SA Health read.
"This was during the time Case B was infectious but prior to staff knowing his positive Covid-19 status. A similar situation was observed again on the same day with a time-lapse of less than 12 minutes.
"Case B opening their door could have resulted in potentially contaminated corridor air either directly exposing Case A or forcing contaminated air into his room, particularly given Case B's room was situated at the end of a corridor and the intervening time period may not have allowed exchange of fresh air to have occurred despite adequate ventilation levels in the corridor."
The revelations over the growing cluster come as Victorians take to the streets to protest the state's latest lockdown laws, following the recent outbreak.
Acting Premier James Merlino yesterday announced a "circuit breaker" seven-day lockdown in response to 26 active cases in the state, initially sparked by another virus leak at a hotel quarantine facility.
One person who contracted Covid-19 in the state has been placed into intensive care.
From 11.59pm on Thursday Victorians can only leave home for five reasons:
• Shopping for necessary goods and services
• Authorised work or permitted education
• Exercise – a 2-hour limit with one other person
• Care giving, compassionate, and medical reasons
• To get vaccinated
Yesterday, Covid-19 Response Minister Chris Hipkins announced an extention to the pause in quarantine-free travel between New Zealand and Victoria.
The extension means the pause will be until at least 7.59pm on Friday June 4. Hipkins said the extension was due to the growing number of cases, more exposure events, and the high-risk nature of some of these events.
Anybody who had been in one of the locations of interest in Victoria couldn't travel to NZ for at least 14 days after they had been at the location, Hipkins said. People who had visited one of those locations could not travel to New Zealand even if they had a negative Covid-19 test, Hipkins said.
Further restrictions, such as pre-departure testing, were being considered, he said.
Anyone who has travelled to NZ after being in the greater Melbourne area since the 20th was now required to be tested and to isolate, director general of health Ashley Bloomfield said. That's in addition to those who travelled to NZ since May 11.
About 5000 travellers are affected by the new restriction.
Melbourne braces for more cases as lockdown begins
Victorian Chief Heath Officer Brett Sutton says he is expecting more cases in the state as Melbourners wake to their first day of a week-long lockdown.
Currently, contact tracers have been able to link all the active cases, but authorities remain cautious of an even bigger rise in cases today.
"It's really hard to know — I don't think we'll see hundreds but I absolutely expect more," Professor Sutton said.
Sutton defended contact tracing after being probed by reporters but admitted the system "does not do magic"
"Contact tracing is an integral part of how to get control. It does not do magic.
"Our contact tracers are identifying and locking down the first ring, second ring and third ring within 24 hours … that is the fastest our contact tracers have ever moved.
"Unless something drastic happens, this will become increasingly uncontrollable."
More than 150 exposure sites
A Thai massage parlour, a cinema and a football club are among new venues added to a list of Victorian Covid-19 exposure sites, which is set to widen significantly to include some 150 places.
As of Thursday night there were 117 sites on the list, but Acting Premier Merlino flagged at a press conference that number could surpass 150 locations.