COOLER conditions overnight have quelled fire activity at a 40,000ha blaze burning south of Traralgon, in Victoria's Gippsland region.

The Country Fire Authority said there was minimal fire activity overnight at the Churchill-Jeeralang fire, which has claimed at least 21 lives in the area, and crews continued to build control lines around the blaze's 135km perimeter.

Firefighters hope milder weather conditions over the next few days will help their efforts to further extend containment lines.

The fire is not a direct threat to communities but residents are being asked to remain vigilant.

Fire crews are working with other agencies to restore power and communications to the affected areas.

Meanwhile, South Australian Country Fire Service crews are bolstering the number of firefighters in the area, providing some relief to exhausted local CFA crews.

The Churchill blaze, which authorities believe was deliberately lit, has devastated local communities at Hazelwood, Jeeralang and Callignee, which was hardest hit with about 12 people confirmed dead in the town.