The severed heads of six state police investigators were found on a public plaza in the northern Mexican state of Durango.
The heads were found yesterday in the township of Cuencame a day after the officers were reported kidnapped.
There was no information on a possible motive, but beheadings are a hallmark of Mexico's brutal drug gang violence.
Meanwhile, in Tijuana the bodies of three young men were found in one neighbourhood. A fourth body was found outside a hospital and a fifth - whose hands and feet were bound - was found dumped near a gas station.
Those deaths came a day after 12 bodies were found in Tijuana, including four that had been decapitated and four men who were killed in a shootout at a popular seafood restaurant.