Purana Taskforce investigators and detectives from the Mornington Peninsula crime investigation unit executed warrants on Mr Gatto's homes on Thursday.

Police spent most of Thursday searching his luxurious holiday house in Thames Place in Mount Martha and his sprawling mansion in Roseburn Court, Lower Plenty.

A large amount of cash as well as a firearm were seized from the Lower Plenty address, police said.

A Victoria Police spokeswoman said the searches related to a "deception investigation".

No arrests have been made.

"The investigation remains ongoing," she said.

Mr Gatto declined to comment when contacted by Fairfax Media.

Mr Gatto, who prefers to be described as a businessman rather than an underworld identity, is a mediator and debt collector through businesses run by associates.

He became known in the wider community during Melbourne's gangland war when many of his associates were murdered in hits organised by drug dealer Carl Williams.

In 2004, Mr Gatto was charged and later acquitted of the shooting death of one of Williams' hitmen Andrew "Benji" Veniamin in a Carlton restaurant corridor.

More recently, he has been targeted by the Australian Taxation Office over a $10 million tax bill and by a Colombian crime gang who put a $200,000 murder contract on him.

Sources told Fairfax Media the gang believed he was responsible for the disappearance of a cargo container from the docks they had imported as a part of a smuggling operation.

"I have nothing to say except I don't have any enemies and I don't know anything about this," Mr Gatto said in August 2015.