The fire at 21 Jackson Street also spread into the roof cavity of 19 Jackson Street, causing damage to that home.

Damage to both houses is estimated in the vicinity of $250,000.

Both houses are managed by Housing Tasmania

Units from Tasmania Fire Service and Glenorchy Police responded to a report of the fire at approximately 4.50am.

There was no one home at either residence at the time of the fire and no person or animals were injured. 

Fire scene examiners, forensics and detectives were on the scene today

The fire is believed to have started at the rear of 21 Jackson Street and while the exact cause is yet to be ascertained, it has been determined as suspicious.

Police are seeking assistance from members of the public or independent taxi drivers who may have observed any suspicious activity in Jackson Street or the adjoining parkland in the early hours of this morning.

Any information can be provided to Crimestoppers on 1800 333 000