NSW Health's "chief virus detective" Jennie Musto - the leader of department's COVID-19 detective team - said thorough interviews conducted with the original Liverpool and Blue Mountains cases enabled her team to pinpoint the Crossroads Hotel as the centre of the state's new COVID cluster which now stands at 34. The source is a man who travelled from Melbourne on June 30 and visited the hotel on July 3.
"One person from the Liverpool Public Unit was interviewed very thoroughly and at the same time the person from the Nepean area was interviewed very thoroughly and he had reported he had been to the Crossroads Hotel. So we went back to the women and asked her if she has been to the Crossroads and she had. And the link was made," she said.
"From there, we've uncovered an additional 32 cases linked to the Crossroads Hotel and from there we've actually learned that the most likely link supported by epidemiology, is that a man from Melbourne came into a workplace in Sydney, and there was some transmission within that workplace and they went to party at the Crossroads Hotel on July 3. This is where it all began.
"So as far as we know, this outbreak is well known to us and we've identified all links, at this point in time, but we'll get new cases and we'll have to identify further links with them and for the contacts and get them all to go into isolation as well."
NSW Chief Health Officer Kerry Chant said there were 13 new cases of the virus overnight, 10 of which are linked to the Crossroads Hotel in Casula.
Six of the cases attended the pub, two were close contacts of those who attended and two acquired the infection at the Planet Fitness Gym.
Since 8pm, she said there had been one extra case detected bringing the linked cluster to a total of 34.
With the outbreak growing daily, Dr Chant said NSW Health was putting together a full list of affected venues on a website, which will list dates and times where any positive cases attended.
New venues, identified since yesterday include the YMCA at Revesby, Western Sydney Leagues Club in Leumeah, Macarthur Tavern in Campbelltown and Woolworths Bowral.
Wests League Club at Leumeah and the Macarthur Tavern in Campbelltown both posted to social media that they had been advised by NSW Health on Tuesday night that patrons who visited their venue had tested positive to the virus.
Dr Chant also reminded the public that it was vital that anyone who attended the Crossroads Hotel between July 3 and July 10 self-isolate for 14 days and get tested for COVID-19.
Staff and patrons who attended Planet Fitness between July 4-10 are also considered to be close contacts, and should self isolate for 14 days and seek testing, she said.
"We've had a very strong focus on the Crossroads Hotel cluster, but it's very important we don't lose sight of the fact that covid could have been introduced in other parts of Sydney," she said.
"This is a stealthy virus and we need to maintain vigilance in other parts of the state. I want you to come forward, if you've got any COVID symptoms, come forward."
NSW Health Minister Brad Hazzard said now was not a time to be complacent.
"When the war time comes back to us it has a bit in last two days, our community steps up," he said, thanking the 3287 people in south-west Sydney who had come forward for testing in the last two days.