The blasts occurred around 5am in the suburb of Vermont after leaking gas accumulated in the below ground drains. The cause of the leak has not yet been identified.

High voltage power transmission lines were threatened by fire at one stage until Metropolitan Fire and Emergency Service personnel brought the fire under control around 7am.

A spokesman said gas had gathered in storm water drains and had to be dispersed with the assistance of gas supplier United Energy.

Gas supplies to homes in the vicinity were cut and surrounding districts were blacked out for some time.