A 23,000-hectare fire raging on Melbourne's northern fringe is expected to take several days to control, Victoria's fire chief warns.
Two hundred fire trucks, backed by 19 aircraft, are fighting the blaze, which began on Sunday in Mickleham and spread to the Kilmore and Wallan regions.
Fire Services Commissioner Craig Lapsley says the blaze moved significantly overnight and got bigger, fanned by winds late on Monday.
"That's a significant operation, and will remain so for the rest of today and tomorrow," Mr Lapsley told reporters in Melbourne on Tuesday afternoon.
"It's proved difficult to get a control line around the entire edge of the fire."
Mr Lapsley says the fire has caused significant concern to the Wallan and Kilmore communities, and houses are believed to be destroyed.
As emergency warnings for the region were downgraded to watch-and-act messages, Mr Lapsley paid tribute to the work done by fire crews to suppress or chase the fire as it ran hard up onto roads.
But people needed to be mindful of smoke billowing into metropolitan Melbourne and central Victoria for days to come, he said.
Watch-and-act messages remain in place for a number of towns, including Wallan, Kilmore, Kilmore East, Darraweit Guim, Bylands and Willowmavin.
The CFA says the fire is not expected to affect Kilmore under the southerly conditions.
But it warns the fire front is active and could change quickly.
Relief centres at Wallan and Seymour have been set up, and residents are advised to keep monitoring the situation.
People travelling in affected areas are warned to be very wary of fallen trees and powerlines, emergency vehicles and changed road conditions.
