The U.S. Justice Department unsealed indictments on Tuesday against four members of one of Mexico’s most powerful drug cartels accused of seeking to purchase arms and ammunition in exchange for drugs in the Czech Republic.

The four alleged members of the Jalisco New Generation cartel, known by its Spanish acronym CJNG, were arrested in the Czech Republic in June, Justice Department officials said.

Two of the defendants — Edgar Alejandro Lopez Velasco, 44, and Jose Miguel Alvarado Morales, 23 — have been extradited to the United States and made a court appearance in Tampa, Florida, on Monday, they said.

Extradition is pending for the other two accused — Noe Diaz Jimenez, 33, and Leobardo Gaxiola Lopez, 63, also known as “Bado,” the officials said.

The four alleged CJNG members are charged with drug importation conspiracy, firearms trafficking and other offenses which carry a maximum sentence of life in prison.

Lopez Velasco and Diaz Jimenez negotiated the sale of weapons in the Czech Republic “to commit acts of violence against rival cartels, civilians, police forces, and military personnel in Mexico,” the Justice Department said in a statement.

“These weapons included different kinds of European machineguns, rocket-propelled grenade launchers, mortar launchers, and accompanying ammunition and ordnance,” it said.

“In exchange for the weapons, the defendants paid in the form of fentanyl and methamphetamine imported into the United States for distribution,” it said.

The United States last week announced charges against several high-ranking members of CJNG and increased reward money for the capture of its leaders to more than $100 million, including  $25 million for information leading to the capture of the cartel’s alleged leader, Juan Carlos Gonzalez, or “Pelón.” According to the State Department, Gonzalez was born in Santa Ana, California, on Sept. 12, 1984.

The State Department said the charges and reward money were aimed at “crippling the organization’s leadership” while President Trump has ramped up pressure on Mexico and other Latin American nations to carry out his security agenda.

CJNG is among eight Mexican cartels designated as foreign terrorist organizations. The group was dealt a blow in February when leader Nemesio Rubén Oseguera Cervantes, or “El Mencho,” was killed by the Mexican military. The U.S. provided intelligence for the operation, which resulted in a burst in violence in the state of Jalisco. 

Last month, the Trump administration slapped sanctions on 50 people and companies linked with the cartel, including González. The sanctions froze assets and blocked U.S. financial transactions with those cited.

In June, the U.S. Treasury announced a new bank alert targeting the cartel.