The seizure of the cocaine occurred in an unidentified foreign country, said the Swiss Federal Prosecutor's Office, which declined to say when the police action took place.
Four people have been taken into custody in Switzerland, the office said, adding that Italian police made further arrests Thursday as part of the investigation.
The statement said the action was part of a larger effort by Italian and Swiss authorities to crack down on a mafia organization active in the southern Italian region of Calabria, the region of Lombardy, where Milan is located, and internationally. The group is similar to the 'ndrangheta crime syndicate operating out of Calabria, it said.
The drugs were discovered in an automobile with plates from the Italian-speaking canton (state) of Ticino, the statement said. Officials at the prosecutor's office refused to provide more details of the cocaine seizure or the investigation.