The State Attorney General’s Office will continue the relevant investigations to clarify what happened and hold accountable whoever is found responsible,” the prosecutor’s

Six severed human heads were found on a road connecting the Mexican states of Puebla and Tlaxcala on Tuesday, Aug. 19. A person called 911 after seeing a head on the side of the road.

Messages are often left on victims' bodies by cartels seeking to threaten their rivals or punish behavior they claim violates their rules.