Mexican authorities have opened an investigation after six severed heads were found on a road linking the states of Puebla and Tlaxcala, in a part of central Mexico that is not usually known for extreme cartel violence.

BBC News reported that the discovery was made early on Tuesday morning on a route between the two states. The local prosecutor’s office said the heads were those of men. Police have not announced a motive and federal authorities had not commented at the time of the report.

The scene has prompted attention because the area is generally seen as more peaceful than Mexico’s most violent cartel battlegrounds. The BBC said the region is not normally associated with the kind of public killings that have become common in parts of the country where criminal groups fight over territory and illegal revenue streams.

Local media reported that a blanket was left at the scene with a warning to rival gangs and a signature attributed to a group called La Barredora, meaning “the sweeper.” The BBC said it was not clear whether that group was responsible, and it noted that a criminal group using the same name operates in the western state of Guerrero. Authorities have not confirmed that link.

The killings come as President Claudia Sheinbaum’s administration continues a crackdown on fentanyl trafficking. The BBC also noted that fuel smuggling remains a major criminal business in the region, generating billions of dollars a year for organized crime groups involved in the trade.

The Tlaxcala case fits a broader pattern of cartel violence that has remained severe in Mexico despite repeated government campaigns against it. The BBC said that in June, 20 bodies, including four decapitated victims, were found in Sinaloa, while seven young people were killed in a church festivity shooting in Guanajuato in May. More generally, the country has seen hundreds of thousands of killings and tens of thousands of missing people since the military was first deployed against gangs in 2006.

At this stage, the immediate facts are limited. Investigators have confirmed the discovery, the sex of the victims and the location, but not the perpetrators or motive. That leaves open whether the attack was tied to turf disputes, smuggling networks or some other criminal message.

What is clear is the symbolic shock of the case. A road in central Mexico that rarely makes international headlines has now become the scene of one of the country’s most gruesome recent crimes, and the investigation is only beginning.

The discovery is also likely to intensify scrutiny of how criminal groups use public violence to send messages far beyond the immediate site of an attack. In cases like this, the lack of an immediate claim of responsibility can be just as revealing as any overt warning, because it forces investigators to determine whether the scene was meant to intimidate rivals, unsettle residents or signal a shift in territory.