The DEA's Arabit testified that the Gulf cartel is now run by a triumvirate.

CNN: Stakes rise as drug war threatens to cross border

"From what we've seen, the Zetas have taken over the Gulf cartel, " analyst Stewart said.

CNN: Stakes rise as drug war threatens to cross border

One side is led by Miguel Angel Trevino, a former member of the Gulf Cartel.

BBC: Q&A: Mexico's drug-related violence

They are now a major criminal group, at war with various old allies, including La Familia and the Gulf cartel.

NEWYORKER: Silver or Lead

His death, along with the 2003 arrest of Gulf cartel founder Osiel Cardenas Guillen, set the stage for the ongoing turf battle.

CNN: Stakes rise as drug war threatens to cross border

Although the DEA and some analysts disagree, others say the Zetas, a paramilitary group of turncoat soldiers and anti-narcotics police, are now running the Gulf cartel.

CNN: Stakes rise as drug war threatens to cross border

In July two Americans, Javier Francisco and Pedro Vargas, were abducted in Austin, Tex. and moved to Dallas by men who authorities say were affiliated with the Zetas, the muscle for Mexico's Gulf Cartel.

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The sweep began after army raids of gangs belonging to the Gulf Cartel, one of Mexico's strongest, led to the discovery of lists of officers in the gangs' pay, according to state judicial officials.

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They beat the Gulf cartel down to insignificance.

NEWYORKER: The Kingpins

But their control over this territory is now said to be facing a challenge from their former allies, the Gulf Cartel, in an alliance with the Sinaloa cartel led by Joaquin Guzman, Mexico's most wanted man.

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