MEXICO CITY — Mexican authorities on Sunday arrested several people suspected of involvement in the killing of nine members of the LeBaron family, the extended clan of American Mormons whose deaths last month drew international attention to rising violence in this country.

The federal attorney general’s office said in a communique that soldiers, Marines, National Guard and other security forces launched a joint operation early Sunday and detained “various individuals believed to be involved” in the killings outside the town of La Mora in the northern state of Sonora.

Authorities have yet to determine who killed nine members of a Mormon family in Mexico on Nov. 4, or their motive, but the victims' family is demanding justice. (The Washington Post)

Officials didn’t provide details, and the attorney general’s office didn’t respond to a request for comment. The newspaper El Universal cited sources as saying three people were arrested in Bavispe, not far from La Mora.

Mexican authorities have said the LeBarons — an extended family of fundamentalist Mormons with dual U.S.-Mexican citizenship who have lived in northern Mexico for generations — appear to have been caught unawares in a conflict between affiliates of the Sinaloa and Juárez cartels that dominate the rural area. Three mothers and six children were slain in the ambush.

Mexican President Andrés Manuel López Obrador faces mounting pressure to rein in the country’s growing violence. In the latest eruption, authorities said at least 19 people were killed over the weekend in a gun battle between the Cartel of the Northeast and security forces in the northern town of Villa Union, about 40 miles southwest of Eagle Pass, Tex.

President Trump said last week he was planning to designate Mexico’s cartels as Foreign Terrorist Organizations, a move that Mexico fears could lead to foreign interference in everything from the business sector to government security policies.

Attorney General William P. Barr is expected to visit Mexico City this week at the invitation of the Mexican government to discuss Trump’s plan.

Julian LeBaron, a family spokesman and longtime anti-violence activist, said the three suspects detained Sunday were low-level “thugs.” He and about 50 other members of his extended family are scheduled to meet with López Obrador on Monday morning.

“We think that’s the reason why they went and picked up these local thugs — so these people can say, ‘Yeah, we did something about this,’ ” he said.

He said the family wasn’t satisfied with the arrests of the triggermen, but wanted the detention of “the people who were responsible for giving the order” to carry out the attack.

The FBI has been assisting Mexico in trying to track down the killers. Last month, Mexican police detained a man believed to have been involved in the attacks, authorities said in the communique Sunday. That arrest wound up providing “critical information and evidence” that authorities pursued.

LeBaron helped lead a march of thousands of critics of López Obrador in Mexico City on Sunday, the first anniversary of the president’s inauguration.

Mexicans were shocked by the attack on the Mormon family, but some have criticized the LeBaron family for calling on Trump to do more to reduce violence in Mexico — including classifying cartels as terrorist groups.

LeBaron acknowledged that many Mexicans worried that such a designation could prompt a U.S. military invasion.

“I don’t think any of us would like to see that,” he said. “But when your sisters and cousins are being murdered, we don’t care where the help comes from.”