The man died at the scene and the other volunteers, three men and a woman, injured in the accident on the Spring Creek Rd at Tatong, north of Mansfield, about 6.30am today.

The CFA confirmed the volunteers were on their way to a fire when the accident happened but did not release members' details.

"We extend our deepest sympathy to the families of the victims involved,'' the statement said.

"A death of a member bears heavily on the broader CFA family, including brigade members."

Two men were flown to Melbourne hospitals in a serious condition and a man and a woman were transported by road ambulance to the Goulburn Valley Hospital in Shepparton.

It is believed two of the injured volunteers went to a nearby house to raise the alarm and a doctor and an off-duty policeman were the first on the scene.

A man, aged in his 40s, was airlifted to the Royal Melbourne Hospital with spinal and chest injuries. Another man, aged 52, was flown to The Alfred hospital with neck, back and head injuries.

Of the other injured volunteers, a man suffered head lacerations and a woman had chest and abdominal injuries.

It is believed the rollover victim is a man aged in his 60s and was driving the tanker.

The Victoria Police Major Collision Investigation Unit is investigating, together with the state coroner.

The CFA will also conduct a full investigation.

The death takes Victoria's road toll to seven, seven fewer than the same time last year.