Team investigating cause of Tas bushfire

Authorities expect to spend several more days battling a bushfire in northern Tasmania.

The fire near George Town has burnt more than 1000ha since it started in a state forest late on Tuesday, where a team is investigating how it began.

More than 100 firefighters are working along with ground and aerial tankers to bring the fire under control.

Crews were granted some reprieve on Friday when wind speeds eased.

"We are expecting that to remain that way into the evening," Tasmanian Fire Service deputy incident controller Neil Brooksbank said.

"It's giving crews the chance to undertake backburning operations, but when they do their backburning there are still considerable flame heights."

On Wednesday, the fire came within a kilometre of homes in Lefroy, prompting an evacuation.

Properties were spared as the fire front turned east, and while it is not heading towards homes or other infrastructure, Mr Brooksbank asked people in the area to remain alert.

Water bombing and backburning will continue on Saturday.

"We are planning to continue into about Tuesday of next week," Mr Brooksbank said.

Thick smoke blankets the area near the fire and is causing traffic problems. Speed limits have been reduced on several roads.

"We've had a few near misses with our appliances and other road users," Mr Brooksbank said.