Relatives began holding funerals Thursday for nine Mormon women and children murdered in northern Mexico, still reeling from pain and anger three days after the massacre.

Long convoys of cars carrying the victims' extended families from other parts of Mexico and the United States wound their way through the rugged mountains to Rancho La Mora, a hamlet of neatly kept ranch-style houses and immaculately groomed pines where one family of victims lived and will now be buried in a small cemetery.

The three women and six children, who had dual U.S.-Mexican citizenship, were killed in a hail of bullets Monday as they drove on a rural road between Sonora and Chihuahua, which border the United States. The case has caused shock on both sides of the border and prompted U.S. President Donald Trump to call for a "war" on Mexican cartels.

The head of the Mexican military's joint chiefs of staff, Homero Mendoza, said authorities now believe the massacre was carried out by a drug cartel based in Chihuahua called La Linea , which means "the Line" in Spanish.

He said investigations indicated the group had sent a squad to the lawless mountain region where the attack occurred to fend off potential incursions by a rival gang, Los Salazar, which is based in Sonora, after recent clashes between the two.

But relatives of those killed rejected the case as mistaken identity as it is alleged by the police, saying they believe their family was deliberately targeted.

"I have to emphasize there was no dueling cartels, and there was no crossfire that our family were caught up in. They were murdered – massacred – solely by one acting cartel from Chihuahua," family member Lafe Langford Jr told AFP.

Adran LeBaron, the father and grandfather of some of the victims, said that according to two of the surviving children, their aunt exited her SUV, arms raised in surrender, only to be mowed down with gunfire.

"So where is the mistaken identity? There was no mistake here," he told Mexican TV network Televisa.

The two families involved, the LeBarons and Langfords, have been targeted by criminal groups in the past.

Benjamin LeBaron, the founder of a crime-fighting group called SOS Chihuahua, was assassinated in 2009 after he led protests over the kidnapping of his 16-year-old brother, who was released after the family refused to pay a ransom.

Harrowing survival story 

The families are part of a large group of U.S. Mormons who emigrated to Mexico in the late 19th century, fleeing persecution for their traditions, including polygamy.

Lafe Langford told CNN that after riddling the cars with bullets and setting one of them alight, the gunmen pulled survivors from one of the cars and told them to flee.

Realizing their shot and bleeding siblings would not make it far, two adolescent children helped the others to hide in the brush. One then went for help, he said.

"The details that are coming from them are just – they're just hard to hear, the heroic actions, the loneliness they felt in those mountains for hours and hours all shot up and wounded, carrying each other in their arms. And just the effort by these six children to survive and come home to their father," he said.

"I mean, what they went through, what they experienced, I don't – we don't have the capacity just to imagine what these children went through."

The victims ranged in age from eight months to 12 years.

Another child, a three-month-old baby, was found wounded but alive on the floor of one of the cars, where her mother had put her when the shooting began.

An eight-year-old girl was also missing for more than 10 hours before being found unharmed several kilometers away.

Information on the case remains murky. Mexican Foreign Minister Marcelo Ebrard said Mexico "will share information" with the U.S. Federal Bureau of Investigation (FBI) in the ongoing probe.

Authorities had initially blamed a different criminal group active in the region, Los Jaguares, but had moved beyond that theory by Wednesday.

Mexican Security Minister Alfonso Durazo said investigators found more than 200 .223 caliber bullet casings manufactured by American gunmaker Remington at the scene. That type of round is commonly used in military-style assault rifles.

He said Mexico and the United States would soon launch a bilateral program "to control arms trafficking from the U.S. to Mexico," adding that 70 percent of the guns linked to crimes in Mexico come from the United States.

The attack has highlighted the lawlessness in much of the border region, the scene of frequent turf wars between cartels fighting over lucrative drug trafficking routes into the United States.

(With input from AFP)