Other crime groups are taking note – and sides – in the dispute.

The Knights Templar, a longtime enemy of Los Zetas with a strong presence in Michoacan state, hung banners across the state Friday belittling Trevino as a “terrorist” and a “military objective” of their group.

Heavy violence linked to Los Zetas has sprung up in central Mexico, leading President Felipe Calderon last week to order the deployment of some 15,000 additional federal police and soldiers to the states of Michoacan, Nuevo Leon, Guanajuato, Zacatecas, San Luis Potosi, Coahuila and Tamaulipas.

Analysts said a splintering of Los Zetas could lead to an uptick in violence as lower-level gangsters sought to snatch turf, smuggling corridors and crime activity.

“When organized-crime groups divide, these divisions are often very violent,” said Jorge Chabat, a security expert at the Center for Research and Teaching in Economics, a Mexico City research center.

Added Logan, the Zetas expert: “When you have the big dogs fighting, it leaves room for the smaller dogs to pick up the pieces and get stronger.”

Any weakening or division of Los Zetas would leave the Sinaloa Cartel under kingpin Joaquin “El Chapo” Guzman the strongest crime group in Mexico. The U.S. Treasury Department in January labeled Guzman "the world’s most powerful drug trafficker.” His group is based in the Pacific Coast state of the same name but it has tentacles around the world.

Nearly a dozen other crime groups occupy smaller niches in the nation’s criminal hierarchy.