NSW Premier Gladys Berejiklian says coronavirus rules across her state are “appropriate”, despite the burgeoning cluster in Sydney and its surrounds.

Ms Berejiklian – who became an official “casual contact” on Thursday after a state government minister’s positive COVID test – has resisted added any more restrictions, despite the growth in the outbreak.

“I was tested very early this morning and isolated and returned a negative test a couple of hours ago and I will continue to follow health advice,” she said.

“Notwithstanding those circumstances, since the pandemic has started, this is perhaps the scariest period that NSW is going through.

“It is a very contagious variant but at the same time we are, at this stage, comfortable that the settings that are in place are the appropriate settings – but that is so long as everybody does the right thing.”

Chief health officer Kerry Chant agreed, saying a lockdown wasn’t required because the state didn’t have large numbers of unlinked cases nor a backlog of contact tracing.

The number of locally acquired COVID-19 cases in NSW linked to the Bondi cluster grew by 11 to 36 on Thursday.

Adam Marshall (left) with Premier Gladys Berejiklian in April. Photo: AAP

Among them is NSW Agriculture Minister Adam Marshall, who was diagnosed after dining in a Paddington pizza restaurant on Monday at the same time as an earlier confirmed infection.

He was with three other Nationals MPs – Trevor Khan, Steph Cooke and Ben Franklin – who are understood to have tested negative.

NSW Health figures show there were 18 new cases in the 24 hours to 8pm on Wednesday, 13 of which were announced earlier.

There were another six cases detected after the 8pm cut-off. They will be included in Friday’s official tally.

Of the 11 new cases, all but one was linked to a known case or the Bondi cluster, with urgent investigations underway into how a man in his 40s caught the coronavirus. He’s the second man in as many days who has contracted it from an unknown source.

Dr Chant said there were “missing links” in the virus’ spread across Sydney.

“This has got out into the community, and there are chains of transmission that we are not aware of. We know that because we have some unlinked cases, so there must be some missing links there,” she said.

“Because of that, we do not know the size of the chains that those missing links have established.”

Mr Marshall confirmed his infection on Thursday morning.

“This morning just after 8am I was formally advised by NSW Health that I had returned a positive test for COVID-19,” he said.

“I’m doing fine and will continue to strictly follow the advice of health authorities.

“I have been in isolation in Sydney since late Tuesday night, when I received a text message from NSW Health.”

Mr Marshall has been isolating at his Sydney flat since Tuesday night and won’t be able to return to his Armidale home for at least 14 days. His ministerial staff are also in isolation.

The four Nationals MPs were in parliament on Tuesday afternoon after attending a party room meeting earlier in the day.

Ms Berejiklian was among many NSW parliamentarians to attend Tuesday night’s Nationals dinner after the state budget was delivered.

“I was there for a short time, addressed the crowd and I didn’t have contact with [Mr Marshall] whatsoever,” she said.

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Parliament staffers were told to stay home on Thursday, and MPs inside the Macquarie Street building were undergoing rapid COVID tests.

Government whip Adam Crouch instructed MPs to “stay put” until they received an update.

“If you are currently in Parliament House remain in Parliament House,” he said.

“If you are not in Parliament House, remain where you are.”

Media and non-essential staff were told to leave, and get tested.

There were just 16 MPs inside the NSW Parliament on Thursday – just enough to pass the 2021/22 budget before the current session is suspended.

“Colleagues are going through that process this morning to ensure that nobody enters the chamber to pass the budget until all of those assessments have been made,” Ms Berejiklian said.

Health Minister Brad Hazzard, who was named as a close contact, has tested negative to the virus. He was out of isolation by midday Thursday.

Meanwhile, school holiday plans are in tatters for many Sydney parents under new travel restrictions.

People living or working in the City of Sydney, Waverley, Randwick, Canada Bay, Inner West, Bayside, and Woollahra local government areas cannot move outside the metro zone unless it’s absolutely essential.

NSW Health has also confirmed fragments of the virus have been detected at sewage plants that service Sydney’s north-west and southern suburbs as well as the Illawarra.

-with AAP