110,000 tests were conducted as Hunter clinics were slammed with demand.

Two new Hunter cases take the region's tally to seven.

"Of the two new cases in Hunter, one is a woman in 60s [and] is linked to the known Central Coast cases announced yesterday," NSW chief health officer Dr Kerry Chant said.

The other is a woman in her 20s who is a household contact of a Newcastle case announced on Thursday.

Dr Chant said high testing rates in the Hunter would help determine whether the week-long lockdown would extend or end next Thursday.

"We need those high testing rates to assure us that we're not missing those chains of transmission," she said.

Queues at testing clinics in the region on Friday are reportedly extending for kilometres in some areas.

The 24-hour period included 291 cases of community transmission.

Many are under examination, Premier Gladys Berejiklian said, but at least 50 were infectious in the community.

"We're likely to see this trend continue for the next few days," Ms Berejiklian said.

"I just want everybody to be prepared for that."

Thursday's figures had been the worst of the pandemic so far in NSW. Alongside plunging the Hunter into lockdown, officials announced 262 infections and five deaths.

Friday's figures added a woman in her 60s from southwestern Sydney who died at Liverpool Hospital to the death toll.

She was not vaccinated, and NSW chief health officer Dr Kerry Chant said 44 of the 50 people in intensive care in NSW had received no vaccines.

Ms Berejiklian also confirmed that Year 12 students in the eight Sydney local government areas locked down would not return to face-to-face learning.

That had been the tenet behind NSW Health seconding Hunter vaccines to the state capital.

Those doses taken from the Hunter would be "replaced in full", Prime Minister Scott Morrison announced on Thursday.

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Friday's case numbers were the first delivered to a Hunter region in lockdown after Ms Gladys Berejiklian made the declaration on Thursday morning.

Dr Chant at that press conference said investigations were ongoing but contact tracers believed the cases were linked to a Blacksmiths gathering and connected to Sydney's western suburbs cluster.

The region's list of exposure sites grew rapidly during the intervening 24 hours to include a Thornton swim school, parts of Charlestown Square and more.

Hunter businesses are bracing for pain, with many in hospitality changing their business model to takeaway.

The University of Newcastle, which on Thursday warned staff and students of a possible exposure at the Callaghan campus' Auchmuty library, was cleared after new information from health authorities.

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