Police were called in to investigate whether Tangara School for Girls in Cherrybrook had broken rules, after media reports alleging social distancing was not being enforced and extracurricular activities and school assemblies were going ahead.

A police spokeswoman on Friday confirmed NSW Health had asked officers to investigate but the probe had concluded and the college had been cleared.

In a statement on their website, the school said the "misinformation" circulating during the "challenging and emotional period" needed to be clarified.

"We have always followed the advice of NSW Health around COVID-19 and will continue to do so," it said.

The outbreak has been linked to a nearby Opus Dei Catholic study centre, Eremeran, which is closed for cleaning after recently hosting five senior schoolgirls.

The school said it plays no role in organising or monitoring attendees at Eremeran which is a third-party provider.

It comes as St Vincent's College in Potts Point became the third independent Catholic school to shut after exposure to the virus, with a student testing positive on Thursday.

It joins Our Lady of Mercy College in Parramatta, which is linked to three cases, and Tangara School for Girls. Both are closed until August 24.

NSW recorded nine new cases in the 24 hours to 8pm on Thursday including a third linked to Liverpool Hospital, and a second connected to Dooleys Lidcombe Catholic Club.

People at the Catholic club during specified hours between August 7 and 10 are considered close contacts and must get tested and self-isolate for 14 days.

Anyone who attended the hospital from August 6-9 is advised to get tested if even mild symptoms emerge.

Of the new cases reported on Friday, one is linked to the Tangara school, three are returned travellers in hotel quarantine and one case has an unknown source.

Police have also issued a number of fresh fines to people and venues for breaching health orders.

A teenager who allegedly punched and spat on a bus driver and a 23 year-old woman who allegedly spat at police and paramedics have been fined.

A Balmain hotel has also copped a $5000 fine for hosting a party, while a Victorian couple were fined for failing to isolate before their ski trip to Perisher.

NSW Labor leader Jodi McKay on Friday upped pressure on government to mandate masks on public transport.

"People are calling for this. The public want it, commuters want it," she told reporters.

But Premier Gladys Berejiklian earlier reiterated that while masks are important, they are a fourth line of defence.

She urged people in southwest and western Sydney, which are linked to several clusters, to come forward for testing and maintain distancing.

"We are concerned there was community transmission we haven't picked up in those parts of Sydney and if we don't, those strains or sources we haven't identified could take off," she told Seven's Sunrise.

Meanwhile, a NSW special commission of inquiry report into the ill-fated disembarkation of the Ruby Princess cruise ship is to be handed to the state government.

The Ruby Princess, which docked at Sydney on March 19, has been linked to hundreds of cases and more than 20 coronavirus-related deaths across Australia.

Australian Associated Press