Anti-gangland detectives have reopened a major cold case investigation 20 years after the robbery of an Armaguard van netted bandits more than $4 million.
Purana taskforce detectives are confident they can solve the case in which robbers posed as road workers on June 22, 1994 holding up traffic on the Monash Freeway before threatening the van's guards at gunpoint and making off with the $4 million.
Armaguard has posted a $100,000 reward for information that could solve the crime.
Victoria Police Assistant Commissioner Stephen Fontana said the detectives had experienced a high success rate solving cold-case murders and sex crimes.
Mr Fontana described the Richmond heist as an "exceptionally well-planned" crime. It is understood at least two suspects went on to become well known figures in Melbourne's underworld.
Mr Fontana said the police wanted to identify two people who tried to launder $40,000 from the robbery in a city bank.
The man and woman were filmed by a security camera trying to exchange the cash two months after the heist, but fled the bank when challenged, leaving the money behind.
Mr Fontana would not reveal how police identified the money but said the couple were "clearly spooked".
"It's definitely solvable," Mr Fontana said. "These people are clearly of interest to us."
An unnamed Melbourne lawyer was charged last week with money laundering in connection with the original 1994 robbery, he said, and detectives are hopeful of further leads.
The road-gang robbery remains one of Melbourne's greatest unsolved crime mysteries.
On the morning of June 22, 1994, the gang, dressed convincingly as roadworkers, complete with overalls and equipment, including a concrete cutter and three vehicles, held up traffic at an off-ramp on the Monash Freeway in Richmond.
Police believe the Armaguard van was tailed from the city by a gang member in a white utility. Once the van was stopped by a "worker" with a stop sign, another gang member opened the back doors with a skeleton key, surprising the guard in the back. He held a gun to his head.
A second robber helped pull the two guards in the front seats through to the rear. All three were tied by the hands and told to "stay down".
The truck was then driven a few blocks to a lane in Richmond, and the crew handcuffed to each other. Plastic bags were placed over their heads. The crates containing the money were unloaded and the guards say they heard a vehicle drive away.
Mr Fontana said detectives were well advanced in their investigations of possible suspects.
"This particular job sparked a lot of interest within the criminal community," he said.
"A lot of people provided information to CrimeStoppers at the time, and I've got no doubt some of that information may have pinpointed who the actual offenders were."
Anyone with information is urged to phone Crime Stoppers on 1800 333 000 or visit the website, crimestoppers.com.au.