MONTERREY, Mexico Mexican drug traffickers have built makeshift car bombs to attack police, troops and rival smugglers as the country's drugs war turns increasingly violent, police said.
Soldiers found two car bombs in a safe house in the city of Culiacan in western Mexico on Monday. One car was packed with cans of gasoline and another stuffed with canisters of gas, police said.
Both devices were wired to be detonated by cell phones, said a police official in Culiacan, capital of Sinaloa state, which is home to one of Mexico's biggest trafficking cartels.
"We believe these two car bombs were being designed to harm the military, the police and rivals," the official said on Wednesday. He declined to be named.
Any use of car bombs would be an escalation of Mexico's brutal drug war that has killed more than 4,200 people since late 2006, when President Felipe Calderon launched a military-backed assault on drug cartels.
Mexico's drug gangs often carry automatic weapons and sometimes wield rocket-propelled grenades but they are not known to have used car bombs before.
The Pacific coast state is home to Mexico's most-wanted kingpin, Joaquin "Shorty" Guzman, who officials say has caused a recent spike in violence in Sinaloa by breaking off an alliance with other local drug lords.
Mexican media said the car bombs may have been made by Guzman's faction although police could not confirm that.
Gunmen shot dead a state police commander, Salomon Diaz, in Culiacan on Wednesday, despite the arrival there of police reinforcements.
More than 300 people have died in drug-related violence in Sinaloa so far this year, including 45 in the past two weeks, as drug gangs fight each other and the army.
Dozens of federal police began arriving in Culiacan on Wednesday to join thousands of troops in place across Sinaloa.
In Ciudad Juarez on the U.S.-Mexican border, drug hitmen killed two unarmed traffic policemen on Tuesday night, prompting 400 colleagues to go on strike.
Striking traffic police held up banners saying "Bathed in blood" and "Guns to defend ourselves" as they protested outside Ciudad Juarez City Hall in a late night demonstration.
(Reporting by Robin Emmott and Ignacio Alvarado in Ciudad Juarez; Editing by Cynthia Osterman)