At least 26 bodies dumped in Mexico's second city
The bodies were found in several vans abandoned around the western city's iconic Millennium Arches monument, together with a message from drug cartels.
An official with the attorney-general's office said the death toll could rise beyond the 26 confirmed so far.
It is the fourth mass public dumping of bodies in regional centers in just over two months, a rash of killings officials blame on a brutal turf war between rival drug cartels which is ricocheting from one side of the country to the other.
Murders in Guadalajara, capital of the state of Jalisco and home to mariachi music and tequila, have spiked in the last year as the Sinaloa cartel's hold on the city has weakened.
The death of key lieutenant Ignacio "Nacho" Coronel in a shootout with soldiers in Guadalajara in July 2010 opened the door to gangs including the Zetas and Milenio, from neighboring Michoacan state, trying to muscle in on the Sinaloans' turf.
Local media said the message found with the bodies, dumped less than 1 mile (kilometre) from the site where the Guadalajara International Book Fair will be held from Saturday, purported to be from the Zetas and was directed at Sinaloa boss and Mexico's most-wanted trafficker, Joaquin "Shorty" Guzman.