A public security specialist at the Mexico Institute of the Woodrow Wilson International Center for Scholars, Eric L. Olson, said too little evidence exists to draw conclusions that the killings are anything but violence between rival gangs.

"We need to take a deep breath," Olson said. "I think the rhetoric is eclipsing our knowledge of what's going on."

As in many of the mass killings in Mexico, forensic teams in Veracruz do not conduct the analyses that would clarify the executions and lead to prosecutions.

"There's no investigation," Olson said, adding that Mexican officials have acknowledged to him that they don't know much about the casualties of Mexico's domestic violence. "When you push them, they are honest: 'We really don't know who these victims are.'"

Doubts about the marines' ability to pacify Veracruz remained palpable Friday, demonstrated by a political cartoon in the El Universal newspaper. It showed a truck carrying marines toward Veracruz, passing roadside signs noting how they had failed to quell violence in Michoacan, Guerrero, Tamaulipas, Nuevo Leon and Chihuahua states in past years.

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