SAO PAULO/MEXICO CITY (Reuters) - Brazilian police have arrested an alleged Mexican drug boss, federal prosecutors said on Wednesday, in a blow to one of the most powerful organizations in Mexico’s criminal underworld.

According to the arrest warrant, police detained Jose Gonzalez Valencia, 42, a leader of the Jalisco New Generation Cartel (CJNG), with the intention of fulfilling a U.S. extradition request.

Once a little-known gang, the CJNG has grown in recent years to challenge the Sinaloa Cartel of captured kingpin Joaquin “El Chapo” Guzman for primacy of the drug trade in Mexico.

Gonzalez Valencia was arrested at a beach resort near the coastal city of Fortaleza and brought to the headquarters of the federal police for the state of Ceará, Brazilian prosecutors said in a statement.

Gonzalez Valencia had been living in neighboring Bolivia for two years after fleeing Mexico and he had entered Brazil as a tourist using a Bolivian passport, the statement added.

An official at the state prosecutor’s office in the western Mexican state of Jalisco said Gonzalez Valencia is the brother of Abigael Gonzalez Valencia, a CJNG leader captured in February 2015.

Jalisco is where the CJNG established itself and serves as a base for much of its operations.

The Jalisco official said Gonzalez Valencia was due to be extradited straight to the United States from Brazil.