A soldier stands guard on Lazaro Cardenas Avenue, where three trucks with more than 20 corpses inside were found early morning, Jalisco State. (HECTOR GUERRERO/AFP/GETTY IMAGES)

The bound and gagged bodies of 26 men were found early Thursday in abandoned vehicles in Guadalajara, a grim sign of escalating mafia violence among gangsters vying for control of Mexico’s second-largest city.

Investigators from the state of Jalisco said that the corpses were stuffed in three vehicles left near the Millennium Arches, a major landmark, and that each of the dead had been shot in the head.

The discovery came less than 24 hours after a similarly grisly scene in Mexico’s Sinaloa state, where the charred remains of 16, some of them handcuffed and wearing bulletproof vests, were left in two pickups. Investigators are looking into a possible connection to Thursday’s crime scene.

“These barbaric acts show that the war between the criminals is getting even more brutal,” said Jorge Aristoteles Sandoval, Guadalajara’s mayor.

Guadalajara has not been among the places considered major Mexican drug-war battlegrounds, such as Ciudad Juarez or Monterrey. But analysts say Thursday’s discovery could signal a new push by the Zetas cartel into territory that has long been the domain of the Sinaloa Federation, the reigning criminal power along Mexico’s western coast.

Luis Carlos Najera, Jalisco state police chief, told reporters that a message was left in one of the vehicles, a white van with license plates from the state of Mexico. But he did not disclose the contents of the message.

Drug-war experts say the Zetas may be muscling into Guadalajara to fight for a bigger piece of Mexico’s billion-dollar methamphetamine trade. Local Sinaloa boss Ignacio “Nacho” Coronel was killed by Mexican soldiers in the city in July 2010. Since then, factional fighting has broken out among groups of gangsters with shifting loyalties and names, such as the Resistance, the New Jalisco Cartel and the Milenio Cartel.

The gruesome spectacle Thursday comes at an inopportune time for Guadalajara, which is two days away from hosting an expected 600,000 visitors for the annual Guadalajara International Book Fair, billed as the largest in the Spanish-speaking world.

Researcher Gabriela Martinez contributed to this report.