Unidentified law enforcement officials said the recent increase in regional violence is likely due to a fight for control of drug trafficking efforts in the region by various criminal organizations, the San Diego Union-Tribune said Thursday.

The 14 people killed Wednesday in Tijuana included Baja California state police agents Marco Cardenas Carrasco and Roberto Elizalde. The two men were killed in separate incidents in the city that took place hours apart.

That same day, the bodies of four unidentified men were found near a community clinic. The cause of death for the men, all between the ages of 20 and 25, was not reported.

Four other men were shot and killed Wednesday night by unidentified assailants, while the bodies of two men were found downtown inside a vehicle, authorities said.

The Union-Tribune said two men were also found decapitated by the Otay Mesa border crossing with a note that referenced the notorious Arellano Felix drug cartel.