NSW has recorded no new locally acquired cases of Covid for the fourth day in a row.
But health bosses are concerned the virus is still being transmitted 'unrecognised' across Sydney as they scramble to find the city's 'missing link' Covid-19 case.
NSW chief health officer Dr Kerry Chant said it was yet to be established how a man in his 50s from Sydney's east dubbed 'BBQ man' become infected with Covid.
Apollo Global Management managing director Tom Pizzey travelled across Sydney last weekend while unknowingly infected with Covid, visiting four separate barbecue stores over the space of a few hours.
He tested positive to the virus on Wednesday and his wife a day later.
Genomic testing has linked the man's case to that of a returned traveller from the US but how the virus was transmitted between them has stumped authorities.
'(The local case's) contact with the infectious person must have been very fleeting,' Dr Chant said on Monday.
NSW chief health officer Dr Kerry Chant (pictured) said the missing link between a returned traveller from the US and a man from Sydney's east was yet to be found
She warned Covid could still be circulating in the community without people realising, adding 'we're not out of the risk period'.
'We are concerned there are chains of transmission in the community that are unrecognised,' she said.
NSW Premier Gladys Berejiklian said authorities had trawled through CCTV and spoke to 'lots of people' in their quest to find out how Mr Pizzey became infected.
'The concern is, if it's one or multiple people, who are those missing links it was a very fleeting meeting,' Ms Berejiklian said.
'That suggests there could be a high level of contagion.'
The window of transmission is likely between April 26, when the traveller arrived and quarantined at the Park Royal Hotel in Darling Harbour, and April 29, when they were moved to special health accommodation after testing positive on April 27.
Tough new restrictions - including masks indoors and on public transport - were extended for a week on Sunday (Wynyard Station pictured)
A nurse collects Covid-19 test samples at the Bondi drive-through testing clinic on May 6, with a huge increase in testing numbers expected thanks to the two new cases
The US traveller was staying in the Darling Harbour hotel, which is not one of the 14 suburbs listed in Mr Pizzey's extensive search for the perfect outdoor cooker on Saturday and Sunday.
Restrictions introduced on Thursday in response to the couple's positive tests and meant to end on Sunday night will be extended for a further week.
Household gatherings remain capped at 20 people, mask usage remains mandatory on public transport and indoor venues such as theatres and aged care homes, and singing and dancing remains mostly banned.
Hospitality patrons are still not permitted to drink while standing.
On Monday, NSW's first mass Covid-19 vaccination hub at Sydney Olympic Park, which will have the capacity to administer 30,000 Covid-19 jabs per week.
The NSW government expects the Homebush hub will have the capacity to It will be staffed by hundreds of medical personnel and operate six days a week from 8am to 8pm in a specially-fitted commercial building.
Ben Shepherd from RFS receives his Covid-19 vaccination at the Olympic Park Vaccination Centre in Sydney, on Monday
For its first two weeks, the hub will be open to people in categories 1a and 1b before expanding to anyone over 50 from May 24.
Ms Berejiklian said she hopes the state can now give out 60,000 vaccines a week, helping to boost Australia's fledgling rollout.
'The mass vaccination centre will be able to administer up to 30,000 vaccines per week once it is up and running, that means around 5,000 vaccinations per day,' Ms Berejiklian said.
'The Centre, combined with the more than 100 NSW Health run clinics and hubs, means NSW Health can administer around 60,000 vaccines each week across the State.'