Mexican authorities said Tuesday that they have arrested a founding member of the notorious Zetas gang who oversaw the smuggling of drugs and migrants in southern Mexico.

Flavio Mendez Santiago, 35, and a bodyguard were captured Monday in the southern state of Oaxaca, from which Mendez allegedly relayed drug shipments and moved migrants from Central and South America north to the U.S. border.

The former soldier allegedly joined the Zetas when the gang was formed in the 1990s by ex-members of elite military units. He was among Mexico's 37 most wanted drug suspects, 20 of whom have been arrested or killed.

He appeared before cameras Tuesday with close-cropped hair and dressed in a black shirt.

The Zetas once served as hit men for the Gulf cartel in northern Mexico, but they broke away early last year in a turf war that has terrorized the border states of Tamaulipas and Nuevo Leon. The gang has branched into migrant smuggling, selling pirated goods, kidnapping and extortion, and it now operates across much of southern Mexico.

Migrant-rights activists say Zeta gunmen kidnap U.S.-bound migrant groups to extort money. In December, Mexican officials said they were investigating the disappearance of about 50 migrants traveling atop a freight train.

The Zetas are blamed for the massacre in Tamaulipas last year of 72 migrants from Central and South America.

Officials said Mendez, also known as "the Yellow One," once served as bodyguard to Osiel Cardenas Guillen, the former chief of the Gulf cartel now imprisoned in the United States. Mexican federal police said they found safe houses in three states and Mexico City that Mendez was using to hide contraband and kidnapping victims.

His alleged activities stretched into Guatemala, to which officials say he traveled in 2008 with the aim of freeing an imprisoned Zeta commander, Daniel Perez Rojas, who was sentenced to 43 years there last year on various charges. As The Times reported in 2009, the spread of Mexican drug gangs into Guatemala and elsewhere in Central America has stirred fears that the criminals could overwhelm historically weak governments.

Guatemalan President Alvaro Colom last month declared a state of siege and ordered the army to crack down in a remote swath along the border with Mexico where drug smugglers have used clandestine airstrips to move drugs.