Victoria Police's professional standards command will oversee an investigation into the overnight death of a man in Echuca, on the border of Victoria and New South Wales.

The 48-year-old Echuca man was sleeping in the back of his white ford falcon ute when the canopy caught alight.

Emergency services were called to reports of a car fire on Ogilvie Avenue at about 4:20am Thursday morning. 

The fire was extinguished but a man was found deceased inside the ute.

The man had been in police custody on Wednesday before his death after providing a positive breath test.

"That was for unrelated traffic offences," Detective Senior Constable Troy Wickham said.

Detective Senior Constable Wickham said the man was local and a homeless. 

"It's not being treated as suspicious," he said. 

"We don't know the exact cause of death but it's likely as a result of the fire." 

Under the Coroners Act 2008, the death of a person recently released from police custody or Corrections Victoria does not meet the definition of a death in custody — unless the person has died from injuries incurred while in custody.  

But due to recent police contact, the investigation into his death and the car fire would be overseen by the Professional Standards Command. 

"We've been speaking to neighbours, canvassing for CCTV, taking witness statements," Detective Senior Constable Wickham said. 

Arson chemists and detectives from Melbourne were on the scene Thursday to help investigate the cause of the fire.

A report will be prepared for the coroner.