CIUDAD JUAREZ, MEXICO -- Police in northern Mexico have received an ice chest packed with four human heads.
The chest that arrived at the Ascencion police station in Chihuahua state was marked "vaccines," but wasn't claimed for a week.
Finally, police opened it and found the heads. The bodies haven't been located.
State prosecutor's spokesman Eduardo Esparza said Tuesday the chest arrived on a local bus line that also has a delivery service.
An envelope with an undisclosed message was found inside.
The heads appeared to be part of a wave of drug-related killings.
Cartels have turned to beheading their enemies as they battle each other for control of lucrative smuggling routes.
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