THE deliberately-lit Bunyip Ridge fire could burn for weeks and endanger more property, a key CFA spokesman says.
The fire has already burned 25,000ha and claimed up to a dozen houses.
However, no lives were lost, stock losses are believed to be minimal and most of the land burnt is state forest.
CFA general manager Westernport area Peter Schmidt told The Weekly Times the fire could burn "until we get four or five inches (100-120mm) of rain."
"This fire fight is far from over, residents still need to remain vigilant," Mr Schmidt said.
The fire started on Bunyip Track last Wednesday. There were several lightning strikes in the area at the time, however the CFA is convinced this fire - the only one it could not control - was deliberately lit.
It spread to Labertouche and Drouin West on Saturday with up to a dozen houses destroyed.
"We had some notice, we ran five community meetings, there were letter drops - people were aware," Mr Schmidt said.
"We had plans in place, that's one of the main factors in there being no life lost here as this fire was every bit as violent as the others."
Labertouche farmer Ron Moore, who stayed to defend his house and chickens on Saturday, said the fire was "horrendous".
"It really was frightening - it came so suddenly, all of a sudden it just went up," Mr Moore said.
"It came so fast it was jumping over itself, there are bits of grass that haven't been burnt - Elvis (the waterbomber helicopter) was right over the top of us.
"We were successful as we had sprays on top of the sheds fed by gravity, it drenched the sheds."
Mr Moore, who is now without power, said the CFA saved his house.
"Nobody would have survived in the whole valley without them," he said.
Mr Moore lost only four of 600 free-range chickens in the inferno.
He is donating the eggs to local charity.
A Tonimbuk landowner said fire came within 500 metres of his house and destroyed his neighbour's home.
As the man spoke to The Weekly Times via telephone, helicopters were filling with water out of his dam to fight a nearby fire.
"(Saturday) was a pretty tense sort of a time ... it was pretty hairy I tell you," he said.
"We stayed here all afternoon, we've got a pump on the dam and sprinklers around the house, a fire unit on back of the ute and gates open so the stock could move."