Thirteen members of an Atlanta drug trafficking cell were sentenced to federal prison for conspiracy to distribute methamphetamine, heroin and cocaine and money laundering, the Department of Justice said Thursday.

According to U.S. Attorney John Horn, the 13 people used passenger buses to smuggle "staggering" amounts of illegal drugs from Mexico to Atlanta.

After swarming one of the buses in Cobb County on May 29, 2014, authorities said the seizure brought the haul of narcotics to at least $10 million. By that point, officials had seized five buses.

The drugs were hidden in secret compartments in the back of the buses, Horn said. Flooring was installed over the compartments and seats were bolted down on top of that, making it hard for officers to detect the drugs.

And aside from the driver and another person who rode on the drug-filled buses to ensure their safe passage, the “buses traveled thousands of miles between Atlanta and Mexico without any paying passengers,” Horn said.

Multiple federal, state and local agencies were involved were involved in the investigation, which started in October 2013 after authorities received a tip and resulted in arrests in Cobb, Fulton and Gwinnett counties.

Over the course of the investigation, authorities seized about 644 pounds of methamphetamine, 37 kilograms of heroin, 27 kilograms of cocaine and $680,000 in drug proceeds.

“This case stands as a disturbing example of Atlanta’s role as a trans-shipment hub for the Mexican cartels as they package drugs for the distribution across the east coast and collect the proceeds for transportation back to Mexico,” Horn said.

Chief U.S. District Judge Thomas Thrash Jr. sentenced the following people:

• Alejandro Carmona, 65, of Arlington, Texas, was sentenced to 20 years in prison, followed by five years of supervised release. Carmona was found guilty of a narcotics conspiracy charge on Nov. 9, 2015, after a week-long federal jury trial.

• Reberiano Arroyo-Santana, 38, of Atlanta, was sentenced to 20 years in prison, followed by five years of supervised release on charges of narcotics and money laundering conspiracy.

• Atenogenes Alvarado-Delgado, 35, of Powder Springs, was sentenced to 19 years and seven months in prison, followed by five years of supervised release on charges of narcotics and money laundering conspiracy.

• Jose Alvarado-Delgado, 37, of Austell, was sentenced to 19 years and seven months in prison, followed by five years of supervised release on charges of narcotics and money laundering conspiracy.

• Ranferi Pineda-Campos, 29, of Lilburn, was sentenced to 11 years and three months in prison, followed by three years of supervised release on charges of narcotics and money laundering conspiracy.

• Alan Arnold Lopez, 26, of Mableton, was sentenced to 11 years and three months in prison, followed by five years of supervised release on charges of narcotics and money laundering conspiracy.

• Jose Antonio Pineda-Maldonado, 24, of Smyrna, was sentenced to 10 years and one month in prison, followed by five years of supervised release on charges of narcotics and money laundering conspiracy.

• Miguel Salinas, 24, of Lawrenceville, was sentenced to eight years and 10 months in prison, followed by four years of supervised release on a narcotics conspiracy charge.

• Blanca Hernandez, 43, of Alpharetta, was sentenced to eight years and one month in prison, followed by five years of supervised release on a narcotics conspiracy charge.

• Rufino Pineda-Perez, 50, of Lawrenceville, was sentenced to six years and six months in prison, followed by three years of supervised release on a narcotics conspiracy and illegal reentry by a previously removed alien charge.

• Jose Ocampo-Jaimes, 37, of Lilburn, was sentenced to five years and 10 months in prison, followed by five years of supervised release on narcotics conspiracy and illegal reentry by a previously removed alien charges.

• Jose Cardenas-Garcia, 50, of Kennesaw, was sentenced to four years and nine months in prison, followed by five years of supervised release on charges of narcotics and money laundering conspiracy.

• Yarely Pineda, 24, of Smyrna, was sentenced to two years and six months in prison, followed by three years of supervised release on a charge of money laundering conspiracy.