Ten bodies were found Thursday in a sports utility vehicle left outside a town hall in a northern Mexican state gripped by a turf war between rival drug cartels, authorities said.
The grisly discovery was made in the early morning in the main square in the city of Zacatecas, state governor David Monreal said in a message via social media.
The corpses showed signs of having been beaten, he said.
Monreal later tweeted that the alleged perpetrators had been arrested, without identifying them.
The Mexican security ministry, which confirmed the number of bodies found in the SUV, said it had sent personnel to help with the investigation into the incident.
The notorious Sinaloa and Jalisco New Generation cartels are fighting in the area for control of drug smuggling routes to the United States, officials and experts say.
Zacatecas state has seen an upsurge in violence in recent years.
In November, the bodies of six people were found hanging from a bridge and a tree in the city of Fresnillo, prompting the Mexican government to send security reinforcements.
Across Mexico, more than 300,000 people have been killed in a wave of bloodshed since the government deployed the army to fight drug cartels in 2006.