A tractor was responsible for the fire which destroyed 88 hectares of grass and two hectares of scrub near Lake Ada, MacGillivray.
The fire started at 11am last Thursday in an area bounded by South Coast Road, Seal Bay Road and Seagers Road.
CFS responded with four appliances, a water bomber and helicopter.
Up to 45 people fought the fire on Thursday, including 30 CFS volunteers, Department for Environment Water and Natural Resources staff and local residents.
Heavy machinery was used to cut a firebreak and a backburn was conducted on the eastern flank of the fire.
The fire was not contained until after dark and fire crews remained at the site all night and on Friday to monitor still-smouldering hay bales during the “catastrophic” fire danger day.