The Criminal Assets Bureau (CAB) says it has concluded search operations in Dublin, Meath, Limerick and Longford.
Assisted by local gardaí and a number of national units, the operation involved the search of 20 residential premises, 18 professional premises and a gym.
Earlier, approximately €15,000 in cash was seized, along with five vehicles - an Audi Q7, Mercedes Vito, VW Golf Mark 7 GTD, VW Golf, and a Honda motorcycle.
Five watches - a Breitling, two Rolex, Cartier and a Legend - were also seized.
Gardaí say a freezing order has also been made in respect of "a substantial amount of money" in a bank account.
A quantity of documents, mobile phones and others are being examined by investigating officers.
However no arrests have been made.
On the operation, Detective Chief Superintendent Patrick Clavin said: "This CAB investigation into an organised crime gang is continuing, today marks a significant development in the progress of this investigation.
"The Criminal Assets Bureau are relentless in their mission to identify the criminally acquired assets of persons and to deny such people these assets.
"The motivation of these organised crime gangs is greed for wealth and we will do all we can to deprive them of this wealth".