Sinaloa state prosecutor Marco Antonio Higuera Gomez said the town of El Platanar de Los Ontiveros had become part of a dispute between the Sinaloa cartel controlled by Joaquin "El Chapo" Guzman, Mexico's most-wanted man, and remnants of the Beltran-Leyva cartel who have allied themselves with the Zetas, a paramilitary organized-crime group founded by ex-members of the Mexican special forces.
"Everything is linked to a dispute for territory and the buying and selling of drugs," he said.
The prosecutor said the nine victims were eating Christmas dinner when gunmen entered the town on foot, surrounded them, and opened fire with assault rifles. They decapitated one victim with a machete and dumped the bodies on field, Higuera Gomez said.
He said the army had set up a checkpoint nearby to hunt for drugs, but the killers had avoided it by entering the town on foot.
Another cartel fight is raging to the south, along the border between the state of Jalisco and Michoacan. At least seven people have been killed in the area since Sunday. Officials in both states said Wednesday they could not confirm local media reports of more than a dozen new deaths in clashes in the area. Michoacan authorities did report the slaying of a mother and her three children in the capital, Morelia, which has been mostly spared the worst of the state's drug violence.
Prosecutors said 41-year-old Maria Elena Lopez Bautista and her 19-year-old daughter and 18- and 13-year-old sons appeared to have been tied hand and foot with wire and burned to death inside their home on Monday.
Officials did not speculate on the motive for the crime, but the border with Jalisco has been hit by clashes between Michoacan's dominant Knights Templar cartel, and the New Generation cartel that operates in much of Jalisco.
Gustavo Ruiz in Morelia, Mexico contributed.