Around 900 people who've come to Tasmania from South Australia in the last seven days are being asked to self-isolate as Health authorities in Adelaide deal with a Covid-19 outbreak.
17 people now have the virus, 15 in one family, up from three yesterday.
The source is believed to a quarantine hotel in Adelaide's C-B-D; members of the family work in aged and healthcare as well as a prison.
A Jetstar flight from Adelaide is due into Hobart on Monday evening.
Premier Peter Gutwein says South Australia will remain classified as low risk for now.
"I'm hopeful that we can get to a point where this cluster can be identified in terms of a geographic location in South Australia, and we can put in place the appropriate ring fencing that's available to us there," he said.
"If we need to elevate to medium risk, then I would have no hesitation to do so."
Jetstar passengers due to leave Hobart on Monday evening on a flight to Adelaide are being warned they may not make their flight.
Deputy State Controller Scott Tilyard says passengers need to stay put.
"They should remain where they are currently residing or accommodated at the moment until they get further advice today," he said.
"We want to minimise the risk of these people moving around in the community until we can get more information and further assess the risk."
Image: Josh Agnew