Cooler conditions on Wednesday had brought relief to firefighters who would work through the day to build earth breaks to fully contain the fire ahead of warmer temperatures forecast for Friday, Morley said.
"We have had very mild, cool conditions overnight which is a great help to the fire suppression effort," he said.
North of Victoria in New South Wales, Australia's most populous state, firefighters were battling 141 fires, including 31 that had not yet been contained.
Fires have burnt through more than 131,000 hectares (324,000 acres) of forest and farmland since Tuesday.
The Rural Fire Service has issued contradictory reports on whether a home was destroyed there.
Fires burning out of control near the towns of Cooma, Yass and Shoalhaven were the most concerning in that state.
Rural Fire Service Deputy Commissioner Rob Rogers said the cool reprieve was expected to be short-lived, with temperatures forecast to climb again by the end of the week.
"We don't need new fires today," he said.
The fires have been most devastating in Tasmania where at least 128 homes have been destroyed since Friday.
Hundreds of people remain at two evacuation centers in the state's south, as fires continue to burn more than 80,000 hectares since last week.
"People have lost everything. We can't comprehend that devastation unless we are in their shoes," Tasmanian Premier Lara Giddings said.
The fires have consumed over 80,000 hectares (198,000 acres) in Tasmania since last week.
Wildfires are common during the Australian summer. Fires in February 2009 killed 173 people and destroyed more than 2,000 homes in Victoria state.
Associated Press writer Kristen Gelineau in Sydney contributed to this report.