AUTHORITIES are investigating the latest in a series of structure fires across the North in the past week, with a Commonwealth Bank fire causing an estimated $300,000 damage.
The fire, in the Elphin Road branch at Newstead, was reported about 11.55pm on Tuesday.
Firefighters contained the blaze to the main office area in the rear section of the building.
They removed roofing iron to prevent the fire from spreading.
The building sustained extensive smoke and heat damage.
North and North-West regional fire investigator Adrian Adams, of the Tasmania Fire Service, said authorities were considering the possibility that an electrical fault had started the fire.
He said there was an electrical appliance within the vicinity of the fire.
Mr Adams said he was waiting to receive CCTV footage, while TechSafe electrical inspectors were still investigating.
Detective Acting Inspector Jonathan Higgins said police were not investigating the bank fire, but were treating the second fire in five days at a South Launceston house as suspicious.
The latest deliberate fire at the vacant house, in Wellington Street, was reported on Tuesday about 9.30pm.
A vandal set fire to a curtain through a window at the front of the house, causing about $200 damage.
A similar blaze at the same property occurred on June 27 about 10.50pm.
An accelerant was used on the earlier occasion and minimal damage was caused.
``Absolutely, we believe they are linked,'' Detective Acting Inspector Higgins said of the two fires at the vacant residence.
There have been 33 arson-related offences reported across the Northern police district in 2013-14, including arson and attempted arson of structures such as houses, schools and sheds.
Police have laid charges in relation to 12 of these offences.
Commonwealth Bank acting regional Tasmanian general manager Lisa Maher apologised to customers for any inconvenience caused by the Newstead fire.
She advised people to use Commonwealth Bank branches in the Launceston central business district, Kings Meadows and Mowbray in the meantime.
Structure fires across the North during the past week:
July 1-2: Commonwealth Bank, Elphin Road, Newstead.
July 1: House, Wellington Street, South Launceston (second deliberate fire).
July 1: Housing Tasmania unit, Arthur Street, George Town (deliberate).
June 30: House, George Town Road, Newnham (deliberate).
June 29: Housing Tasmania unit, Allwinton Court, Waverley (suspicious).
June 28: Shed, Sinclair Street, Bicheno.
June 27: House, Wellington Street, South Launceston (deliberate).
June 25-27: Shack and farm building, George Town area (deliberate).
June 24: House, Barretts Road, Karoola.