MEXICO CITY, Sept 23, (AP): US Ambassador Ken Salazar rejected accusations by Mexico's president that the US was partly responsible for a surge in cartel warfare in northern Sinaloa over the weekend. Sinaloa has been eclipsed by violence as two warring factions of the Sinaloa cartel have clashed in the state capital of Culiacan in what appears to be a fight for power since two of its leaders were arrested in the US in late July.

"It is incomprehensible how the United States can be responsible for the massacres we see in different places,” Salazar said in a news conference in Chihuahua on Saturday. "What is being seen in Sinaloa is not the fault of the United States." The arrests startled many because it appeared that the son of notorious drug kingpin Joaquín "El Chapo” Guzmán abducted an elder cartel figure, Ismael "El Mayo” Zambada, and flew them both to the US to be detained.

Such a violent outburst was expected in the wake of the arrests. As the warring cartel factions and authorities have clashed in firefights, helicopters regularly circle overhead and military rove the streets of the capital. Families have said they are scared to send their children to school. Meanwhile, bodies have appeared across the city, often left slung out on the streets or in cars with either sombreros on their heads or pizza slices or boxes pegged onto them with knives.

The pizzas and sombreros have become informal symbols for the warring cartel factions, underscoring the brutality of their warfare. Local authorities said that as of Friday at least 53 people had been killed and 51 others have gone missing in Sinaloa state since the fighting started. On Thursday, Mexican President Andrés Manuel López Obrador blamed American authorities in part for the bloodshed.

Asked at his morning briefing if the U.S. government was "jointly responsible” for this violence in Sinaloa, the president said, "Yes, of course ... for having carried out this operation.” "If we are now facing instability and clashes in Sinaloa, it is because (the American government) made that decision,” López Obrador said.