A Country Fire Authority spokeswoman said the Harrietville fire broke containment lines about 4pm on Thursday and was heading in a south-easterly direction, creating spot fires about 0.5 kilometres ahead of the fire front.

The CFA has issued an emergency warning for Mount Hotham, Hotham Heights and Dinner Plain, citing a risk to lives and homes.

Residents who have not evacuated are being advised to seek shelter and the CFA says there is a risk that telephone lines may be compromised.

Mount Hotham spokeswoman Gina Woodward said the main concern late on Thursday night were two spot fires on the skifields near lift infrastructure and a workshop area.

"We've got the snow guns running, which are like giant sprinklers in summer, to help get these fires under control," she said.

"This came so fast this afternoon, there wasn't a whole lot of warning. We evacuated staff last week, had advice to safely return on Saturday afternoon, and here we are again.

"The fires are in the skifield area so there's no infrastructure damage at this point and our teams are working hard to ensure that doesn't happen."

A CFA spokeswoman said about a hundred firefighters were battling the spot fires in the skifields and another hundred firefighters were on their way.

Four water-bombing helicopters were also used to fight the fires for about 20 minutes before nightfall.