Crews work to put out last of Tas fires

Tasmanian bushfires that have sparked community alerts in recent days are now contained, authorities say.

Only one blaze at Osterley in the state's Midlands continues to carry a public warning, but poses no threat to private property, the Tasmania Fire Service reports.

More than 70 bushfires have started across the island state since Saturday, fanned by periods of hot and windy conditions and the danger was rated "catastrophic" on Tuesday.

Firefighters continued to combat or monitor 22 fires on Thursday afternoon.

"They've all got containment lines around them and the crews are just working to extinguish them," a TFS spokesman told AAP.

The blaze near Osterley started on Saturday and has burnt through more than 2600 hectares of mostly remote bushland, destroying two sheds and a car.

A fire that came within minutes of homes, north of Hobart near Tea Tree on Tuesday, has since been downgraded and back burning is in progress.

"There may be visible smoke and fire activity within the burnt area for some time," the TFS said on its website.

Near Orford on the east coast, a fire that had burnt for more than four days was contained late on Wednesday.

The cause of each blaze will be investigated, and senior fire officers believe many of the fires that started on Saturday were caused by a flare-up of smouldering patches left over from private landowner burn-offs.