(Rewrites throughout with details on victims, gang battle, quotes from relative, officials)
By Lizbeth Diaz
BAVISPE, Mexico, Nov 6 (Reuters) - The nine American women and children killed in northern Mexico were victims of a territorial dispute between an arm of the Sinaloa Cartel and a rival gang, officials said on Wednesday, and may have been used to lure one side into a firefight.
Members of breakaway Mormon communities that settled in Mexico decades ago, the three families were ambushed as they drove along a dirt track in Sonora state, leading to U.S. President Donald Trump urging Mexico and the United States to "wage war' together on the drug cartels.
Accounts emerging of Monday morning's slayings detailed the heroism of a surviving boy who walked for miles to get help for his siblings, and heavy gun battles in the remote hill area that lasted for hours into the night after the attack.
"We were deliberately targeted, used as bait to lure one cartel against another," said Lafe Langford, a cousin of some of the victims, who grew up in the same Mormon village.
Hitmen opened fire on the three mothers and 14 children traveling from a village in Sonora to meet with relatives in neighboring Chihuahua state and Phoenix, Arizona.
When the killers struck, the families were spread out along a 12-mile (20 km) stretch of road near the border of the two states, according to Mexican authorities and the families.
As bullets began to pummel the first car, a white Chevrolet Suburban, Christina Marie Langford Johnson stepped out waving her arms to show that they were not gang members, according to a family statement based on reports from the surviving children.
Christina was shot dead. Her baby, Faith, survived the attack in a child seat that her mother appeared to have placed on the floor before she got out.
Gunfire also ripped into a second white Suburban, carrying Dawna Langford and nine children, some two kilometers back, authorities said. Dawna and two sons were killed.
Reuters video of the vehicle showed more than a dozen bullet holes in the roof and sides of the vehicle. Inside, blood was smeared across seats and children's toys.
A third car, 18 km behind, was shot up and burst into flames, killing Rhonita Miller and her four children.
DRUG CARTEL RIVALRY
Some hours earlier, the La Linea arm of the Chihuahua-based Juarez Cartel sent gunmen to defend the state border area, after attacks in a nearby town by the Los Salazar faction of the rival Sinaloa Cartel, a top Mexican general told reporters.
The Juarez Cartel wanted the Sinaloa Cartel off its turf, General Homero Mendoza said. While no official explanation has been given for the killings, Mendoza and other officials say the gang may have mistaken the families' SUVs for those of its rival.
The Sinaloa and Juarez Cartels have for years been at odds over lucrative routes in the border region used to move cocaine, heroin and other narcotics into the United States. Mexico has long requested that Washington do more to control demand for drugs. Mexico has unleashed its military against cartels since 2006 but despite the arrests or killings of leading traffickers, the campaign has failed to reduce violence. In fact, it has led to more killings as criminal groups fight among themselves.
Mendoza said the Miller car appeared to have exploded because of the gunfire. More than 200 spent shell casings were left behind.
Relatives of the victims rejected the mistaken identity theory, arguing that shell casings and personal belongings found near the torched car suggest the attackers came close and made sure everybody was dead before igniting the vehicle.
"They shot us up, burned our vehicles to send a smoke signal into the sky," Langford said, arguing that the gang's goal was to draw the Sinaloa gunmen into battle.
The families' account of the attacks and subsequent efforts to recover the surviving children include reports of shooting from the hillsides that continued well after dusk.
A man was arrested in a nearby town in a truck carrying a .50 caliber Barrett rifle and other military-grade weaponry, but the government later said he was not linked to the murders.
The Mexican government countered Trump's call by urging Washington to help stop the flow of American weapons south of the border, and Security Minister Alfonso Durazo said Remington shell casings of U.S. origin were found at the crime scene.
"That's one of the most relevant details we can give you," he told reporters at a news conference on Wednesday.
When the gunmen shot dead his mother and two brothers, the uninjured 13-year-old Devin Langford hid six surviving siblings nearby and walked for 14 miles (23 km) to find a rescue party.
"After witnessing his mother and brothers being shot dead, Dawna (Langford)'s son Devin hid his six other siblings in the bushes and covered them with branches to keep them safe while he went for help," the families said in their statement.
For 11 hours, relatives had no idea about what had happened to their loved ones.
The youngest of Devin's siblings, 9-month old Oliver, was shot in the chest; 8-year-old Cody had bullet wounds to the jaw and the leg, while Xander, 4, had been hit in the back. Brothers Trevor, 11, and Rogan, 2, lay dead.
When Devin failed to return, his 9-year-old sister Mckenzie, who was grazed in the arm, went after him and walked 10 miles before getting lost in the dark. Search parties later found her, the families said. Another sister, Kylie, was shot in the foot, while sibling Ryder was uninjured.
Nearby were the bodies of the Miller family, including 8-month-old twins Titus and Tiana.
"All shot and burned in their vehicle," the statement said. "Only ashes and a few bones remain." (Reporting by Andrew Hay in Canon, New Mexico and Lizbeth Diaz in Bavispe, Mexico; Additional reporting by Frank Jack Daniel, Sharay Angulo, Noe Torres and Dave Graham in Mexico City; Editing by Grant McCool)