THREE vehicles were travelling side by side moments before a crash which killed two people, a witness told police.
Two men, believed to be from the Bendigo area, died when their car hit a tree on the Calder Highway at Glenalbyn on Saturday.
A 35-year-old woman and 67-year-old man, who had been travelling in a separate car, were taken to hospital with serious injuries.
They remain under police guard.
Detective Senior Sergeant Gerard Clanchy said a witness made a triple-0 call with reports of erratic driving moments before the crash.
The witness told police the vehicles had been overtaking in a “leap-frogging” manner before two vehicles collided and crashed.
“We need to get to the bottom of what happened,” he said.
“This is something that should not have happened.
“Two people have lost their lives through driving that is just unacceptable.
“We have early reports that the vehicles were overtaking each other described in a leap-frogging motion.
“We are appealing for anybody who may have witnessed that to contact Crime Stoppers.”
Detective Senior Sergeant Clanchy said the occupants knew each other.
“My understanding is that there is some connection to those people but we are still trying to establish what that connection is,” he said.
Police are investigating whether speed was a factor.
Marks were left on the road and a blue Ford station wagon, which the deceased men had been travelling in, was severely damaged.
A 51-year-old Wedderburn man, who had been travelling in a third vehicle, has been arrested and is assisting police at Bendigo station.
“At this stage he has been (co-operative),” Detective Senior Sergeant Clanchy said.
Sergeant Mick McCrann said the man had not been charged.
Detective Senior Sergeant Clanchy said police are believed to have been dispatched to the area prior to the crash.
Road rage will also be investigated as a potential cause.
The road was closed after the incident and is not expected to open until late Saturday.
Anyone with information can call Crime Stoppers on 1800 333 000 or visit crimestoppers.com.au