A solid containment on any of the bushfires burning near Fingal has not yet been achieved.
The Tasmania Fire Service continued battling the conditions with backburning on Thursday.
Two spot fires have been caused as a result of the main fire, that was deliberately lit, at Mangana.
The Mangana fire has burned about 7500 hectares spanning 45 kilometres and the Mount Malcolm fire has a perimeter of 26km and has burned 21 hectares.
TFS' incident controller Stephen Lowe warned things could get worse.
"If the fire gets into the Douglas Apsley [National Park] it's highly likely it would push out to the east coast before we could contain it," he said.
"We have a strategy for that if the fire does push into the Douglas Apsley."
He said Saturday's conditions are not looking favourable.
"Each night we get what's known as funneling effect as the sea breeze drops down off the mountain and pushes down into the valley. The fire does a lot of weird things up until midnight."
Crews are "resourced up", Mr Lowe said, with a significant amount of machinery and 10 aircrafts on standby.
"We have multiple inter-agency four crews on the fire so we are well resourced for what we have," he said.
The national park will be closed.
TFS is also keeping a close eye on a fire on Flinders Island.
Crews have been working on containing the fire for the past three days. The cause of the fire is also being investigated.
An emergency warning was also put in place for Glenlusk in the state's south on Thursday. The Pelham fire remains at advice level.
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