Boxes with a chilling threat were left Sunday outside a government building in Chilpancingo, Mexico. The boxes contained severed heads and a threatening note was left nearby calling the people “traitors” and “blackmailers.”

In nearby streets, three bodies were also found.

The latest violence, in the Mexican state of Guerrero, follows years of drug-related violence in the state. The severed heads created havoc in the city as police the struggled to identify the victims. The gang was identified as Los Jefes, Spanish for The Bosses.

The state has been at the center of fighting between some of Mexico’s most notorious gangs as they fight for the best drug routes along the Pacific coast, according to the BBC. Aside from those larger organizations, smaller groups also operate there, kidnapping people and demanding ransom. The drug violence in Mexico has resulted in the deaths of tens of thousands of people in the past 10 years.

Guerrero is also the site where 43 students disappeared in 2014, attracting international coverage as the high-profile case unveiled that government officials and police were cooperating with organized crime groups.

There are signs that violence in the country could be getting worse, as well. Earlier this year, the country’s homicide rate reached its highest level in two years. At that time, Guerrero was displaced at the top of the list of reported homicides by state. There were 55 homicides a day in February, a record rate dating back to January 2014.

Throughout the country, the first two months of the year saw 3,158 homicides, an 11 percent increase compared to that same period in 2015. Experts at the time estimated that 2016 could result in a homicide rate of 20 per 100,000 residents. That’s much higher than the United States just to the north, which posted a 51-year low homicide rate of 4.5 per 100,000 residents in 2014.