A 450-hectare fire at Stoneyford east of Cobden has been contained.
The CFA this afternoon said small pockets of land were still burning today and crews were strengthening established containment lines.
That work was expected to continue overnight and into tomorrow.
A CFA spokesman said there was no threat to communities, but residents should continue to stay informed and monitor conditions.
"Smoke will be visible from nearby communities and roads.
"Please travel to the local conditions and with headlights on," the CFA said.
Speed reductions have been imposed at the Cobden-Stoneyford Road juncture with Ansons and Koallah Roads
The CFA advised people to avoid those areas if possible because fire crews were still active in the area.
CFA officials and police have labelled the cause of the fire as suspicious.
CFA and Department Of Environment and Primary Industries investigators and Warrnambool police crime investigation unit detectives examined the fire scene today to try and determine a cause.
Detective Acting Sergeant Ryan said the fire was believed to have started in at least three places just to the west of Scoullers Road, off the Cobden-Stoneyford Road near Stoneyford.
"It is unknown how the fires started. There's nothing to confirm it was deliberately lit but the cause of the fire is definitely suspicious," he said.
"We looked at one site late last night and the CFA investigator described it as highly likely as one of the seats of the fire," he said.
"While the cause of the fire is suspicious, at this stage we do not know how it started. Whether it was deliberate or some other unknown means we are unsure as yet."
Detective Acting Sergeant Ryan said the fire started about 2.40pm on Wednesday and he called for any witnesses who saw anything unusual in that area, or a vehicle, to contact the Warrnambool police station CIU or Crime Stoppers.
On Wednesday night more than 30 CFA units and a number of aircraft attacked the fire that was swept along by strong south east winds.
The fire has blackened about 450 hectares of farmland near the Cobden-Stoneyford Road and is burning in stony terrain.
At one stage it threatened three houses near the corner of Scoullers Road and the Cobden-Stoneyford Road.