Police investigate the scene where 12 bodies were discovered
The authorities in the Mexican border city of Tijuana have found 16 bodies in 24 hours, in what police believe is part of a wave of drug-related murders.
Twelve of the bodies were found on a patch of wasteland near a school just before it opened. Most showed signs of having been bound and tortured.
A wave of murders linked to the drug trade has claimed the lives of more than 3,000 people in Mexico this year.
Tijuana is a key area for smugglers aiming to get drugs into the US.
City officials suspended lessons at the school near where the bodies were found.
Tijuana police spokeswoman Prisna Perez said some of the bodies were partially clothed and showed signs of torture.
Shortly after the discovery, four other bodies turned up on another patch of wasteland in a residential area.
Both sets of bodies had notes attached suggesting they were victims of gang violence related to the drugs trade.
Two more bodies were discovered late Sunday next to a factory on Sunday, although officials believe they were victims of street crime rather than drug related.
Almost two years ago President Felipe Calderon launched a nationwide battle to take back territory controlled by some of the world's most powerful drug gangs.
But the cartels have responded with unprecedented violence - including kidnappings and killings that have sparked public outrage and huge street protests.
The country has overtaken Colombia and Iraq for the number of kidnappings.