UPDATE: REPORTS are circulating that two firefighters have been killed at Harrietville in Victoria's alpine region.

Nine News reports two Department of Sustainability and Environment firefighters were killed near Harrietville south of Bright.

A CFA spokeswoman said there had been a serious accident at Harrietville and no details had yet been confirmed.

The DSE has confirmed there has been a serious accident at the Harrietville – Alpine North fire.

An Ambulance Victoria spokesman said paramedics received a call at 4.12pm and were advised a tree had fallen on a vehicle at Pheasant Creek Track in Selwyn.

“We were advised there were two injured patients,” the spokesman said.

“Two helicopters and several road vehicles were sent to Beveridge Station at Porepunkah, near Harrietville.”

Wodonga firefighter David Brown tweeted that he was mourning the loss of two firefighters.

“It will be with a heavy heart that I return to Hotham tomorrow,” he said.

“Mourning the loss of 2 DSE firefighters this afternoon.”

The Australian Workers Union Victorian secretary Cesar Melhem has also confirmed the death of two DSE firefighters. 

"Our members have confirmed that two firefighters unfortunately lost their lives," Mr Melhem told AAP.

Mr Melhem said the deaths were a shattering loss for the firefighters' families, their workmates, the union and all Victorians.

"These DSE firefighters work in the most horrific conditions imaginable, away from the big centres, out in the bush, and with very little recognition for their heroic contribution to this state," Mr Melhem said in a statement.

"They have died heroes, which will be small comfort to those that grieve them."

The union said the identity of those who had died had not been confirmed.

"The priority at this stage will be to recover the bodies because they're still behind the fire lines and attend to the rest of the firefighters making sure all of the support has been provided to them," Mr Melhem said.

The DSE and CFA had earlier said firefighters were making the most of mild weather conditions working around the clock to control hotspots and build containment lines around the fire.

The Harrietville fire has burned 27,000 hectares since it was started by lightning on January 21.

Another Victorian DSE firefighter died while working on bushfires in Tasmania last month.

Peter Cramer, a DSE firefighter and CFA volunteer from Tyers in Gippsland, was part of a contingent of more than 70 Victorian emergency services workers sent to Tasmania to help fight the fires.

Mr Cramer, 61, died on January 13 at Taranna, east of Hobart, while working on foot to identify potential containment lines on the southern boundary of the Forcett fire about two to three kilometres from the active fire edge.