The U.S. State Department warned its citizens about traveling to parts of Mexico including Cancun and Playa del Carmen, as homicides rise at resorts popular with American tourists.

The advisory issued on Tuesday upgraded the warnings for two states, Quintana Roo and Baja California Sur, saying turf wars between crime gangs have led to a surge in violence. The only warning for Quintana Roo in a December statement was about lack of cellular and Internet service in some areas.

The expanded travel advisory hits right at the heart of a tourism industry that brings in $20 billion a year for Mexico. The state of Quintana Roo, where the resorts of Tulum and Cozumel are also located, gets 10 million tourists a year, a third of the national total. The warnings come as homicides in Mexico are set to rise to their highest since at least the turn of the century. Quintana Roo alone has seen 169 murders this year.

“Shooting incidents, in which innocent bystanders have been injured or killed, have occurred” in both states, the U.S. warned. “While most of these homicides appeared to be targeted criminal organization assassinations, turf battles between criminal groups have resulted in violent crime in areas frequented by U.S. citizens.”

While Quintana Roo’s advisory is now stricter, it isn’t included among the most dangerous spots in Mexico, where U.S. government personnel are told to defer non-essential travel. That restriction is reserved for parts of Chihuahua, Coahuila and Colima states, among others.