The most recent grisly find was in the town of Fresnillo near a warehouse where police had recently seized drugs, Zacatecas state government said in a statement.
The badly decomposed bodies were left there several days ago, it said.
Zacatecas is a largely rural state that has seen a rise in drug cartel violence in the last two years as the Zetas gang pushes south from its home base along Mexico's border with Texas.
Drug violence has killed more than 47,500 people since President Felipe Calderon launched an offensive against Mexico's cartels when he took office in December 2006.
Gruesome mass killings continue in parts of northern and western Mexico. On Thursday, police in neighbouring San Luis Potosi state found the bodies of 14 men stuffed into an SUV near a gas station.
Federal police said on Friday a man who escaped from the SUV told investigator he played dead and then escaped when the gunmen stopped at a gas station. He hid in nearby hills until state police officers helped him and took him to a hospital.
The federal agents were on an anti-drug operation when they came under fire from gunmen hiding in the hills of the village of Holanda, part of the municipality of Apatzingan, the department said.
Assailants opened fired and threw grenades at federal agents who arrived in the area by land and air to help their colleagues. They also blocked highways and streets with cars set on fire to hinder the deployment of federal police, it said.
The department didn't say what group is suspected in the attack but the Knights Templar cartel, a cult-like Mexican drug gang, is known to operate in the area.
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