More than 200 firefighters with 54 trucks and two waterbombing aircraft tackled the Malmsbury fire, which also threatened neighbouring Drummond and Taradale.

Its cause was eventually traced back to a combination of high winds, a falling branch and clashing powerlines.

CFA incident controller James Dalton said winds in the area were gusting up to 100kmh, blowing the branch onto local powerlines.

"Given those conditions and the indicators left behind by the fire, it is clear that it had reached its full momentum and temperature within 30 minutes of ignition," he said.

CFA fire crews spent Friday carrying out blacking works and patrolling potential hotspots at both sites.

The fire burnt 285 hectares of mainly public land while the Woodend blaze burnt 193ha of mainly private land.

At Woodend, the fire swept to within one kilometre of the western edge of the town.

Department of Sustainability and Environment state duty officer Dennis Ward said cooler weather on Thursday night helped control the fires.

However, Mr Ward said continuing hot weather this week meant people needed to remain vigilant.