Chief Health Officer Dr Kerry Chant and Health Minister Brad Hazzard will appear before the upper house's COVID-19 oversight committee later today.
Dr Chant will be questioned over the advice she provided to the NSW government about when Sydney needed to go into lockdown during the latest outbreak.
The inquiry will focus on Dr Chant's advice in the early days of the Delta outbreak in June.
"We will hopefully be asking the questions 5½ million have been wanting answers to. It starts with what was the public health advice the government received in the first week and a bit after the initial community transmission and before the citywide lockdown," inquiry chair Greens MP David Shoebridge said.
It comes as the state recorded 283 new locally acquired coronavirus cases yesterday, with at least 106 circulating in the community during their infectious period.
More areas are now in lockdown as the Delta variant spreads north, including Tamworth and four North Coast councils including Byron Shire.
An entire apartment block in Penrith – one of the western Sydney LGAs recently identified as being of concern – is now in lockdown.
NSW Health on Monday evening listed the Astina Apartments as a close contact exposure site for all of last Tuesday, Wednesday and Thursday, meaning visitors must get tested and quarantine for 14 days regardless of the result.
The same advice applies to visitors to Newcastle West's Air Locker Training Kotara, north of Sydney, for some of Monday and Tuesday, August 2 and 3.
Yesterday Premier Gladys Berejiklian said she would prioritise the return of freedoms but only when cases reached a lower level.
"I'm sure if you asked the majority of people in our state 'would you look forward to more freedoms than what we have now' I think the answer would be 'yes'," she said.
Those freedoms would be given at the expense of borders opening with other states.
"At the moment nobody from NSW can travel anywhere anyway. So isn't it better for our citizens, for our health and safety and wellbeing, to fight for our citizens to have those freedoms?"
Ms Berejiklian says high vaccination rates were crucial to the lockdown easing on August 28.
But in Sydney's south-west, which remains the epicentre of the pandemic, vaccination rates remain low.