MEXICO CITY—Authorities in northern Mexico say volunteer searchers have found 11 bodies in clandestine burial pits just a few miles from the U.S. border. The government of Sonora state said late Monday the bodies included nine men and two women. Sonora has been locked in a bloody three-way turf battle between rival factions of the Sinaloa cartel and gangs allied with fugitive drug lord Rafael Caro Quintero. On Tuesday, those gangs left three bodies—one hanging from a highway overpass—in three different cities in Sonora. The bodies were left near banners accusing authorities of protecting one of the Sinaloa factions. In the case of the clandestine graves, investigators used backhoes Sunday and Monday to excavate a series of pits, many holding several bodies, in San Luis Rio Colorado, across the border from Yuma, Arizona. The state prosecutors’ office said the bodies were “badly decomposed” and would be subject to genetic and …