Authorities in central Mexico discovered six severed heads on a road connecting the normally quiet states of Puebla and Tlaxcala early Tuesday morning.
The area is not typically associated with cartel-related violence.
Police have yet to provide a motive for the killings or identify which criminal group might be responsible.
Local media reported that a blanket was found at the scene bearing a message warning rival gangs, apparently signed by a group called “La Barredora,” meaning “the sweeper.”
It shares the name of a little-known criminal organization operating in Guerrero, but it remains unclear if they carried out the attack or why.
According to news agency AFP, the local prosecutor’s office confirmed the heads found in Tlaxcala belonged to men and said an investigation has been launched.
Aside from drug trafficking, the region also struggles with fuel smuggling, or “huachicolea,” a lucrative criminal enterprise generating billions of dollars annually.
Federal authorities have so far not commented on the incident. The killings occur amid President Claudia Sheinbaum’s administration ramping up efforts against fentanyl trafficking.
Puebla and Tlaxcala are generally spared the extreme cartel violence seen in other parts of Mexico.
By contrast, in June, 20 bodies, including four decapitated, were discovered in Sinaloa, a state plagued by gang wars.
In May, seven Mexican youths were killed in a shooting at a Catholic Church festival in Guanajuato.
Violence between cartels has escalated in recent years, with hundreds of thousands killed and tens of thousands missing since the Mexican government first deployed the military against gangs in 2006.
