Tasmania Fire Service senior firefighter Adrian Adams said crews were alerted to the structure fire at Hudson's Prospect Plumbing Supplies in Donalds Avenue at 3am.

"En route we received another message indicating a second triple 0 call had been made," Mr Adams said.

"Upon arrival, we ascertained 80 per cent of the building to be engulfed by flames."

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Mr Adams said that for that reason the 13-member crew - assisted by five volunteers - focused on protecting the surrounding buildings.

"Due to the intensity of the fire, the building could not be saved," he said.

Gas bottles outside the building were venting due to the heat, adding to the volatility of the situation.

Crews with four fire trucks and an aerial platform battle the 10-metre flames for an hour before the blaze was brought under control.

"Our priority was to contain the fire and we were able to achieve that goal safely," Mr Adams said.

A forklift and several hot water cylinders were among the items destroyed.

TFS crew members remained onsite until after noon yesterday. Business general manager Andrew Howell yesterday described the fire as an inconvenience and apologised to his customers.

"We will be rebuilding as soon as we can, and in the meantime will be operating out of our site at 7 Donalds Avenue," Mr Howell said.

Crews were called to another two fires in the Prospect area about 1.30am, resulting in damage to a motor vehicle and a rubbish bin.

•Firefighters from the TFS's Launceston brigade were called to a structure fire in Gray Street, Riverside, just before 7pm. The fire was extinguished quickly with damage kept to a minimum. The cause is being investigated.