Five severed heads were left in a bag near a Mexican primary school, the latest example of the ruthless violence plaguing the country.
Police were not able to determine if the grisly find, in an Acapulco neighborhood, was connected to extortion threats against teachers. Some 140 schools have closed their doors in recent weeks due to frightened teachers going on strike, according to The Associated Press.
The men's heads were in a sack inside a wooden crate placed near the school, officers said. Messages threatening three aleged drug traffickers were also found in the bag.
Police had earlier discovered five headless bodies in another part of the city. Drug gangs have waged bloody battles for control of the Pacific Coast resort city. With the government cracking down on the drug trade, gangs are turning to extortion, according to the BBC. Last month, dozens of teachers in Acapulco said gangs had threatened them with violence if they did not hand over half their salaries.
It was unclear who was behind the killings or what the motive was.