TIJUANA — The gruesome discoveries this week of five bodies, four of them decapitated, have shattered a period of relative calm and revived concerns that organized crime groups are escalating their battle for control of this border city.
Two bodies were found Monday morning on a hillside, one with its head placed on its upper back.
Three more bodies were discovered Tuesday morning in an illegal dump.
Their heads, charred from gasoline burns, were placed at their feet, according to the Baja California state attorney general's office.
Authorities have not identified the victims.
The attacks recalled the decapitations two years ago of three Rosarito Beach police officers.
Authorities believe the recent victims may have been associates of the reputed leader of the Arellano Felix drug cartel, Fernando Sanchez Arellano, nicknamed El Ingeniero -- The Engineer.
Printed on the shirtless victims' backs was a taunting message: "We are people of the weakened engineer."
Violence had declined significantly in recent months, and Alberto Capella Ibarra, Tijuana's secretary of public security, discounted the significance of this week's killings, comparing them to Los Angeles-area gang slayings that are barely noticed.
"The only difference here is how dramatic the deaths are," Capella said in an interview in his downtown office.
But Capella and others conceded that the savage nature of the crimes could signal a deadlier phase in the drug war as the Arellano Felix drug cartel fights rivals.
The cartel, once among the most powerful in Mexico, has been weakened in recent years by arrests and killings of its top bosses.
Sanchez Arellano is said to have assumed control when his uncle, Francisco Javier Arellano Felix, was captured in 2006.
In April, a gun battle between groups headed by Sanchez Arellano and a rival faction left 13 dead and appears to have split the cartel into two camps.
The head of the rival group, Teodoro Garcia Simental, moved to the state of Sinaloa, where he may have forged ties with a cartel based there, said Mexican law enforcement sources who spoke on condition of anonymity as they were not authorized to talk publicly on the subject.
The recent deaths could be a sign that Garcia or one of his underlings may have launched an offensive to push out Sanchez Arellano with the help of powerful allies from Sinaloa.
Such a scenario, some fear, could turn Tijuana into a battleground on par with the northern state of Chihuahua, where more than 800 deaths this year have been linked to drugs, the most of any Mexican state, according to a report by the Trans-Border Institute at the University of San Diego.
The Chihuahua death toll grew higher Tuesday when gunmen killed five people at a family gathering at a ranch.
Also this month, cartel gunmen killed 13 people at a party in the tourist town of Creel, and eight people during a prayer service at a Ciudad Juarez drug rehabilitation center.