Police found 16 corpses in the Mexican border city of Tijuana on Monday, 12 of which were stacked together in a vacant lot, authorities in the northwest state of Baja California said.
The discovery of the apparent murder victims was the latest in a wave of violence across northern Mexico near the US border with rival cartels battling for control of drug smuggling operations.
In Tijuana authorities are focusing on the Arellano Felix brothers, also known as the Tijuana cartel, as prime suspects.
More than 3,000 people have been reported murdered so far this year across the country, according to estimates by Mexican journalists.
In August, 12 bodies were found decapitated in Merida, capital of the southern state Yucatan.
Earlier this month 24 corpses were found together, handcuffed and shot, in the federal district of the capital.
In an effort to clamp down on the violence the central government has deployed 36,000 military troops throughout the country.