Tasmania Police say one of the fires was deliberately lit, which has caused another blaze through spot fires.

On Wednesday, crews from across the state used whatever resources were available to them to contain the fire, which hasn't got that much larger since Monday's initial fire.

Residents also helped.

Ruth Miller has lived in the town since 1976, and said she had never seen a fire so close. She spent the day outside moving her sprinklers to stop spot fires.

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She lives across the road from what is normally the town's football oval. But for the past three days it's been the landing base for the numerous helicopters. At one stage there were five choppers fighting the fire.

Next to the football oval is a river the helicopters are filling up their bladders with. Next to that is the fire. It is metres away from her home and Ms Miller said she is ready to evacuate when told to do so.

"I didn't realise how dry it was until I saw all the embers on the ground," she said.

"I'm just trying to keep everything wet. It's too close to home."

She says residents and emergency services have lost their patience after learning the fire was deliberate.

"We've all had enough. We're fed up. It's putting lives at risk," she said. "It was pristine bush land. Look at it now. That won't recover for years."

She said if anything, it's brought the Fingal community closer together.

Some Mangana residents and their pets are sleeping in their cars, and while one said it's not the New Year's they were hoping for, they're thankful to be alive.

Tasmania Police Northern Commander Brett Smith said the behaviour of the arsonist was irresponsible.

He said investigations were occurring in regards to a number of fires over the past months.

"Police have reason to believe the main fire, as well as other fires in the area have been deliberately lit," he said.

"Bushfires are devastating, destructive, and in this case has displaced people from their homes. Someone must know something about who is responsible for this fire."

Investigators are urging anyone in the community with information about who is responsible for these fires, or who saw anyone acting suspiciously around the time the fire started, to come forward.

Commander Smith said police had been investigating the possibility of fires being deliberately lit "for some time".

On Tuesday, police and Tasmania Fire Service held a community forum to tell residents.

Police will have a significant presence in the area during the following weeks and say they are taking this matter "particularly seriously".

Six detectives were in the area on Tuesday and are hoping residents will come forward with hard evidence, such as CCTV footage, for police to charge the people possibly responsible.

Commander Smith said there were a lot of upset people within the community as a result of the announcement.

"It has a massive impact on the community itself and the residents at that community meeting yesterday were quite understandably concerned," he said.

"We are really hoping the people who have information will have the courage to come forward.

"We're pretty confident people not only know who the offenders are, but have seen things that will connect people to the fire."

Other residents have helped the fight too, with neighbours working to also put out embers landing in the town. One said he was defending his house and the neighbour's who had gone away for the weekend.

"The kids thought it was a bit of fun to put the spot fires out, but they don't realise how dangerous it was," they said.

Resident Malcolm Saunders, who has lived in the town for about 69 years, said he witnessed trees exploding on Monday evening.

"This bushfire, it's cleaned the place out. I don't think I can ever remember fires out through here this big," he said.

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