The office of Mexico's Attorney-General says that a man has been arrested in connection with the killing of nine members of a Mormon community in 2019.
The man, who has only been identified as Alfredo L, was detained in Ciudad Juárez, one year to the day after the murders of the three Mormon women and six children in the state of Sonora.
He is the second person to be arrested in connection with the case.
The family of the victims says there are more than 100 suspects in the case.
What's the case about?
Three women and their 14 children - all part of the LeBaron family, a group of US Mormons who settled in northern Mexico - were travelling in a convoy of three cars from the community of La Mora in Sonora state to the neighbouring state of Chihuahua.
They were ambushed by gunmen who opened fire on the cars. The three women and six of the children were killed.
One of the surviving children, a 13-year-old boy, hid his siblings in the bushes and walked 23km (14 miles) to raise the alarm.
When members of the community arrived at the scene, they found one of the cars burnt out with some of the bodies inside.
In another car, seven-month old baby Faith Langford was found alive in her baby seat in the footwell of the car.
Her mother, Christina Lanford Johnson, was one of the three women killed. She was reportedly gunned down after she had stepped out of the car with her hands raised to try show that those inside were women and children.
Who was behind the attack?
One of the theories put forward is that the attack was a case of mistaken identity.
The area in which the shooting occurred is being fought over by two rival gangs, La Línea and Los Chapos, and it is thought that lookouts for La Línea mistook the convoy of three SUVs the women travelled in for an attack by Los Chapos.
The statement by the Attorney-General's office about the arrest of Alberto L did not make clear which of the gangs he is suspected of belonging to, simply alleging that he is "a member of a criminal organisation present in the north of the country".
Adrian LeBaron, the father of one of the three women killed, expressed his disappointment at the fact that only two suspects are currently in detention in connection with the murders.