Just when you thought it was safe to travel to Acapulco, think again.

Mexican police have found five severed heads in front of a primary school in the Pacific coast resort of Acapulco.

It’s unclear whether the gruesome discovery is related to extortion threats that led about 140 elementary schools in the city to close temporarily earlier this month after teachers and parents decided it wasn’t safe enough to start classes.

State police say the five heads were found early Tuesday in a sack, along with a handwritten message threatening three alleged drug traffickers.

The heads all appear to be of men. But some of the five headless bodies found elsewhere in the city a day earlier were too badly burned to immediately determine their gender.