It took the Wynyard Fire Brigade just five minutes to arrive at the Housing Tasmania unit - one of 11 at the corner of Bowick and Lockett streets - but it was still too late.

A cigarette was likely to have caused the accidental fire which started on or near the woman's bed, police said.

Neighbour Lois Whyte heard the woman's smoke alarm and saw smoke coming from the roof.

She tried in vain to help the woman, then rang emergency services.

She went back to try again, but the fire was too fierce for her to get close.

"... then I couldn't get in, the windows were all blowing."

Other neighbours tried to fight the blaze with hoses, but that did not help much.

"It was useless, there was (virtually) no pressure," next-door neighbour Adam Hurding said.

Neighbours said the victim, 77, had mobility problems and was legally blind. She lived with her little dog, who survived.

"She was a happy sort of person ... bed ridden," Mrs Whyte said.

Police are yet to name the woman.

The local fire brigade was called to the fire at 10.19 and arrived five minutes later, with the Somerset brigade following shortly afterward.

"When Wynyard arrived, it was fully involved," fire service district officer Rob Deverell said.

Wynyard police sergeant Nigel Sheahen said police were contacting the woman's relatives.

He said they would not be able to do a final formal identification until they received forensic results.

A fire service investigator estimated damage at between $180,000 and $200,000.

The fire, at East Wynyard, was within about 50 metres of the Table Cape Primary School's Bowick St campus.

It is understood the children were indoors at the time and not aware of the fire.