The bodies of 11 men and a woman were found dumped in an empty lot next to a Tijuana elementary school Monday morning, an hour before children were scheduled to arrive.
City officials suspended classes after finding the victims, most of whom had been bound and tortured.
Minutes after the grisly discovery, four other bodies were found in another empty lot in Tijuana. Two other bodies were discovered late Sunday in a lot next to a factory.
Investigators believe 16 of the victims were killed by warring drug gangs. The other two were victims of street crime.
Afghan policeman kills U.S. soldier
An Afghan policeman opened fire on U.S. troops at a police station, killing one American soldier and wounding three, officials said Monday.
An American commander said U.S. forces in the station in eastern Afghanistan then killed the policeman.
The shooting took place in Paktia province Sunday after American troops and Afghan police brought suspected militants to the station. The policeman wounded three U.S. soldiers, one of the detainees and an Afghan interpreter working for the Americans, officials said.