A massive gunbattle between rival drug and migrant-trafficking gangs near the U.S. border left 21 people dead on Thursday, prosecutors said.
The clash occurred in a sparsely populated area about 12 miles from the Arizona border — a prime corridor for immigrant and drug smuggling.
Mexican media said the gunbattle was on the road connecting Altar and Saric.
Sonora's Attorney General's Office said in a statement that nine people were captured by police at the scene of the shooting, six of whom had been wounded in the confrontation. Authorities at the scene found seven rifles.
El Dario said after the fray police seized 19 high-powered weapons and 11 late-model vehicles.
Officials did not say why the gunfight had broken out, but powerful and well-armed Mexican gangs often fight for control of smuggling routes into the United States.
In a city on another part of the U.S. border, gunmen killed an assistant attorney general for Chihuahua state and one of her bodyguards.
After being chased by armed assailants through the darkened streets of Ciudad Juarez, the vehicle carrying Sandra Salas Garcia and two bodyguards was riddled with bullets Wednesday night.
Arturo Sandoval, a spokesman for the Attorney General's Office, said the second bodyguard was seriously wounded.
Salas was responsible for evaluating the work of prosecutors and special investigations units in Chihuahua.
On Thursday, unidentified men also left a head outside the house of the favorite for Ciudad Juarez mayor, Hector Murgia, who is running for Mexico's main opposition Institutional Revolutionary Party, or PRI, before the vote in 12 states Sunday.
Drug violence has killed more than 4,300 people in recent years in Ciudad Juarez, which borders El Paso, Texas.
More than 23,000 people have been killed by drug violence since late 2006, when President Felipe Calderon began deploying thousands of troops and federal police to drug hot spots.