Twenty-one people have been killed in Mexico following a gun battle between suspected rival drug gangs near the US border. Two groups authorities believe were involved in drug and human trafficking clashed in a deserted area about 12 miles south of the border, Sonora State Police spokesman Jose Larrinaga Talamantes.
Prosecutors in northern Sonora state say the fighting occurred on Thursday in a sparsely populated area about 20km from the Arizona border.
The state attorney general's office said in a statement that nine people were captured by police at the scene of the shootings, six of whom had been wounded in the confrontation.
Authorities at the scene found seven rifles.
"Details are sketchy as it's is a very far away area from the capital of the state, but police say two gangs are fighting for control of the area. It is a very lucrative transit point for drugs and migrants crossing the border into the US," she said.
"Drug traffickers are also involved in the human trafficking business, so that's why they are fighting for control of territory."
The Mexican Army, state police and federal police responded to the area after the shootout, which witnesses said happened about 4 a.m. Thursday (7 a.m. ET). Investigators were still searching for others involved later Thursday, Larrinaga said.
The latest violence comes after Rodolpho Torre, a leading candidate for governor in the northeastern state of Tamaulipas, was assassinated on Monday.
Felipe Calderon, the Mexican president, said the ambush was carried out by drug cartels looking to sway the vote which takes place in 12 states on Sunday.
On Thursday, unidentified men left a severed head outside the house of Hector
Murgia, the favourite for mayor of Ciudad Juarez, who is running for Mexico's main opposition Institutional Revolutionary Party [PRI].
Across the country hundreds have been killed as the drug war increases in intensity.
At least 23,000 people, mainly traffickers and police, have been killed in drug-related violence since Calderon launched an army-led offensive against drug gangs after taking office in December 2006.