Tasmanian contact tracers are racing to assess travellers from NSW who have entered the island state since December 11, as a COVID-19 cluster in Sydney grows.
Public Health deputy director Scott McKeown said on Friday about 1000 people a day had come into Tasmania over the past eight days.
Between 20 to 30 of those are believed to have been in Sydney's northern beaches, where the cluster is located.
The Tasmanian government has deemed the northern beaches local government area and several other Sydney locations high-risk areas.
Anybody who spent time in a high-risk area will not be allowed to visit Tasmania unless approved by the state's deputy state controller.
More broadly, NSW residents wishing to travel to the island state have had their Tas e-Travel passes cancelled and must confirm they have not visited the areas when they reapply.
Premier Peter Gutwein said Tasmanians returning from a high-risk area would be able to quarantine at home, or an approved residence.
If personal accommodation is unavailable, government lodging can be arranged.
"I understand for many people this may put plans for the upcoming season in doubt," he said on Friday.
Anyone who has arrived in Tasmania since December 11 and who has visited the northern beaches or certain locations in Kirribilli, Peakhurst and Penrith must self-isolate immediately and contact the public health hotline on 1800 671 738.
Dr McKeown said the fate of the Sydney to Hobart yacht race, due to start Boxing Day, is yet to be determined. Organisers are continuing to plan for the prestigious race to go ahead.
"We really need to see what happens between now and the commencement of the race," Dr McKeown told reporters.
It comes as other states restrict entry from NSW, with Western Australia reintroducing mandatory 14-day quarantine for all NSW arrivals from midnight.
Queensland is ordering any travellers who visited the northern beaches since December 11 to get tested and isolate for the next fortnight.
Victoria and the Northern Territory have also imposed restrictions.
The northern beaches cluster has grown to 28 cases and is expected to increase.
Dr McKeown says there will be further updates as NSW authorities continue to respond to the situation.