MTA Police and Nassau County District Attorney Kathleen Rice will hold a 1 p.m. news conference to discuss the arrests.
They will also display the gear recovered from the suspects that was used to skim the machines.
The suspects were recently arrested, and two have already been arraigned. The investigation is continuing for other suspects.
Police say the suspects struck at six to eight stations on Long Island and the Bayside station in Queens. Investigators are still going through the evidence to determine how many victims the scam netted.
Authorities first became aware of the skimming scheme last month when one MTA customer found a small video camera on the floor at one of the train stations. That prompted MTA police to start checking hundreds of other machines at other LIRR stations.
They found a small hidden camera on the underside of a black metal strip planted across the top of each ticket machine with an adhesive. The black metal strips blended in perfectly and looked like they were in fact part of the machine.