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The officials also said the gunmen made comments before opening fire on the agents indicating that they knew who their targets were. San Luis Potosi police said that at least 10 assailants were involved in the shooting and that the agents’ bullet-riddled vehicle was found off to the side of the highway.

Mexican authorities said Mr. Rejon Aguilar, known as “El Mamito,” had been a member of the Mexican special forces but deserted his unit in 1999. He was described as a founding member of Los Zetas, which initially served as armed enforcers for the infamous Gulf Cartel.

Los Zetas have since split with their former bosses and have been engaged in brutal turf wars for control of cocaine-, marijuana- and heroin-smuggling routes into the United States.

Mexican authorities said Mr. Rejon Aguilar was “connected to the attack” against the ICE agents, noting that he was in charge of operations for the Zetas in San Luis Potosi when the American agents were ambushed.

“When Jaime Zapata was murdered on February 15, ‘El Mamito’ was in San Luis Potosi, coordinating actions perpetrated by the Zetas,” said Ramon E. Pequeno, anti-drug division chief of Mexico’s federal police.

Mr. Pequeno called Mr. Rejon Aguilar’s arrest “a triumph” for the Mexican government.

“El Mamito’s capture is emblematic because he was one of the original Zetas,” he said.

Mr. Rejon Aguilar also is being investigated in the killing of dozens of Central and South American migrants, whose bodies where found on a ranch in the northern Mexican state of Tamaulipas just 100 miles south of the U.S. border.

In the past few months, Mexican authorities have unearthed more than 140 bodies from mass graves in the state of Tamaulipas. Many of the victims were kidnapped off buses and killed when they refused to work for the Zetas. Tamaulipas, in northeastern Mexico, is across the border from Brownsville, Texas.

Violence has been commonplace in Mexico since a raging war between drug-smuggling cartels began in 2006, claiming 35,000 lives. The Los Zetas cartel is considered among the most violent drug gangs now seeking to control lucrative smuggling routes into the U.S.