Mexican authorities have arrested a suspected leader of the country's Zetas drug cartel.

Officials said Thursday that Alfredo Aleman Narvaez, known as “The German Commander,” was arrested at a horse race he organized in the northern state of Zacatecas. He is accused of trafficking marijuana both in Mexico and the United States.

The announcement comes one day after U.S. authorities uncovered a major drug smuggling tunnel under the border with Mexico and seized 14 tons of marijuana during searches related to an investigation.

Officials say the cross-border tunnel was about 400 meters long and connected warehouses in Tijuana, Mexico and an industrial park in the San Diego, California area. The investigators also say the tunnel, which was discovered Tuesday, was equipped with structural supports, electricity and a ventilation system. The multi-agency San Diego Tunnel Task Force is conducting the investigation. Two arrests were made in the case.

In November of last year, raids on two tunnels linking California and Mexico netted a combined 50 tons of marijuana on both sides of the border. They were equipped with rail systems, lighting and ventilation. The tunnels are among dozens that have been discovered in recent years.

Mexico is in the midst of brutal drug gang violence that has claimed an estimated 45,000 lives since President Felipe Calderon took office in late 2006 and began a crackdown on the cartels.