Several Mexican tourists were evacuated from small hotels in a faded neighborhood once frequented by Hollywood stars.
Mexican police say they have found three severed heads in plastic bags in the Pacific coast resort of Acapulco.
The Guerrero state Public Safety Department says in a statement that the black plastic bags were discovered outside a tunnel that connects central Acapulco to the outskirts of the city. It says the victims were male.
A note left at the scene said the beheadings were revenge for the killing of a man who was shot dead during an attempted kidnapping.
The police statement says the heads were discovered Sunday, the same day armed men attacked a police station in the city, wounding an officer. The same suspects later shot at a house, wounding two people at the residence.