At least nine American citizens, including a mother of seven and her 8-month-old twins, were killed in a roadside ambush on a highway in the Mexican state of Sonora on Monday.

Three vehicles were attacked and set on fire by gunmen believed to have ties to organized crime, family members told NBC News.

Among those killed were Rhonita Miller, 30, and her 8-month-old twins, Titus and Tiana, as well as two of her older children, Howard Miller, 12, and Krystal Miller, 10, family member Kendra Lee Miller told NBC News.

Also killed were Christina Marie Langford Johnson, 29; Dawna Langford, 43; Trevor Langford, 11; and Rogan Langford, 2, Miller said.

Rhonita Miller, 30, and her 8-month-old twins were among the nine Americans killed in a roadside ambush in Mexico. Courtesy Kendra Miller

Christina Marie Langford Johnson's 7-month-old daughter, Faith, somehow survived a volley of gunfire after her mother put her on the floor of her SUV in her carseat, Miller wrote in a detailed Facebook post on Tuesday morning about the attack.

The three women were each driving in separate vehicles after deciding to travel in a convoy together because there had been "some issues with the mafia," Miller said.

"From what I understand, mafia from Chihuahua state, competing mafia from Chihuahua — we’re from eastern Sonora — they had come in and basically went into all-out battle,'' Miller told NBC News. "These women were somehow caught up in the middle of it, but also murdered in cold blood."

Five other children suffered bullet wounds and survived, Miller said. Kylie Langford, 14, was shot in the foot, Cody Langford, 8, was shot in the jaw, Xander Langford, 4, was shot in the back, Mckenzie Langford, 9, had a bullet graze her arm, and 8-month-old Brixon Langford was shot in the chest.

Devin Langford, 13, was not injured but walked 14 miles to get help after hiding his bleeding siblings in the bushes, Miller said.

Rhonita Miller also has three other children who did not accompany her on the trip, according to Miller.

Eight-month-old twins Titus and Tiana Miller were among multiple children who were killed or shot in a roadside ambush in Mexico. Courtesy Kendra Miller

All nine of those killed were American citizens living in La Mora, an agricultural community descended from Mormon settlers that is about 70 miles south of the Arizona border. Many residents have dual citizenship in America and Mexico.

"I am shocked it even happened here," Kendra Miller's father, Kenneth Miller Sr., told NBC News. "We're out in the sticks. We’re nothing nobodies. There’s a drug war going on … the fight for control of the drug monopoly and trafficking has been going on for years. It’s just happened to hit us now."

The family has lived in the area for 50 years, with many currently working as pecan farmers. However, they are considering leaving after the violent attack.

"There's been a lot of talk that none of this is worth it if we lose someone,'' Kendra Miller said.

Rhonita Miller was on a shopping trip to Arizona with her family, while the others were going to Chihuahua to visit family, Miller said.

"As I understood it, there was a number of people that were in a motorcade, there were several families traveling to another community, and not very far out of La Mora then their family came under attack and there was a number of vehicles, three of them in particular, that were shot and one of them was set fire,'' Willie Jessop, a relative of one of the victims, said on TODAY Monday.

Mexican national police and military forces are searching for the gunmen. President Donald Trump also tweeted about the incident on Tuesday morning.

A wonderful family and friends from Utah got caught between two vicious drug cartels, who were shooting at each other, with the result being many great American people killed, including young children, and some missing. If Mexico needs or requests help in cleaning out these..... — Donald J. Trump (@realDonaldTrump) November 5, 2019

....monsters, the United States stands ready, willing & able to get involved and do the job quickly and effectively. The great new President of Mexico has made this a big issue, but the cartels have become so large and powerful that you sometimes need an army to defeat an army! — Donald J. Trump (@realDonaldTrump) November 5, 2019

"A wonderful family and friends from Utah got caught between two vicious drug cartels, who were shooting at each other, with the result being many great American people killed, including young children, and some missing,'' he wrote. If Mexico needs or requests help in cleaning out these monsters, the United States stands ready, willing & able to get involved and do the job quickly and effectively."

The attack is the latest in a string of violence across the country, including an attack in the state of Michoacan last month in which 14 police officers were killed.

Cartel gunmen also attacked the city of Culiacan last month and forced the government to release the son of drug kingpin Joaquin "El Chapo" Guzman Loera after authorities captured him earlier in the day.

A spokesman for the U.S. State Department told NBC News they are aware of the reports of the attack on the American families but had no further comment.