A Montrose man, 30, is being interviewed by detectives from the anti-bikie Echo Taskforce in relation to firearm and drug matters. No further arrests are expected.
Six firearms – a mixture of longarms and handguns – and a boat have also been seized.
"We've been at pains to point out that the victim has no criminal association and no association with the Mongols," Walsh said today.
She said the murder charges are "of the highest order" and police allege the two men were responsible for the fatal shooting.
When asked if Virgona's death was a case of mistaken identity, Walsh said she "wouldn't want to speculate" as the two accused had only just been interviewed.
"We work so hard to get to resolution for these jobs, there's just no way we want to jeopardise that by compromising the criminal justice process," she said.
At a press conference earlier this month – where Virgona's teenage son, Luca, spoke beside his mother, Antonietta – investigators said they were unable to establish a motive for the brutal killing.
"The tragic events that have occurred have removed an innocent and well-respected man from this Earth," Luca Virgona said.
"My greatest role model in life is now gone and we are left to pick up the pieces of our broken family."
Police said Virgona's killers waited for him to leave his home in Croydon and followed him in a Mercedes-Benz sedan, which was later found torched in Mooroolbark.
The duo are thought to have switched to a getaway car, a Volkswagen Amarok utility, before dumping it and running into a park.
Police released images of a distinctive Nike top, believed to have been dropped by one of the suspects.
Walsh said the operation was the result of months of hard work by multiple police units.
"We understand that any time there is an incident involving illicit firearms, particularly one that results in someone being killed in this way, there is enormous concern in the community," she said.
"Today's activities should send a strong message, especially to those involved in this type of criminal activity, that it's absolutely not acceptable and Victoria Police is committed to tracking down and targeting those people willing to commit these offences."