A U.S. federal grand jury has indicted 12 suspects, including six current or former airport baggage security inspectors, in connection with a massive cocaine smuggling operation at the international airport in San Juan, Puerto Rico.

U.S. Attorney Rosa Emilia Rodriguez-Velez, in a statement Monday, said the case is built on evidence that the defendants smuggled suitcases containing as much as 15 kilograms of cocaine through the airport’s Transportation Security Administration (TSA) security system. Other defendants include at least one former airport security manager and suspected couriers.

Between 1998 and 2016, the statement alleges, the defendants helped smuggle 20 tons of cocaine through San Juan Luis Munoz Marin International Airport.

The six TSA workers, who face a minimum sentence of 10 years in prison, were supposed to provide security and baggage screening for checked and carry-on luggage placed on outbound flights. 

However, the statement describes one worker, Javier Ortiz, as picking up suitcases he knew contained cocaine from drug couriers at airline check-in counters. The statement alleges he would place those suitcases into X-ray machines monitored by TSA co-conspirators, who cleared the suitcases for designated flights.

The statement alleges another suspect, identified as Tomas Dominguez-Rohena, would then take the suitcases to their designated flights, making sure no narcotic K-9 dogs or law enforcement personnel were present as the contraband was loaded onto the aircraft.

Authorities say the probe was launched in January 2015 to detect and prosecute drug traffickers using the San Juan facility and other airports on the island as key bases for cocaine distribution abroad.

The U.S. statement said the ongoing probe also is targeting illegal weapons, human cargo, counterfeit documents and the trafficking of illegal profits from illicit activities.