Mexico drug war: Tamaulipas murder suspect 'confesses'
The Mexican army says a man arrested two days ago has confessed to involvement in the murder in Tamaulipas state of 72 migrants last year.
Officials say Abraham Barrios Caporal told them he and other alleged members of the Zetas drug cartel killed the migrants because they suspected them of belonging to a rival cartel.
Soldiers arrested Mr Barrios Caporal in the southern city of Coatzacoalcos.
He said he had moved there from northern Tamaulipas to evade capture.
The Mexican army said they had arrested Mr Barrios Caporal, also known as Erasmo, on 28 June along with at least two other alleged members of the Zetas cartel.
The soldiers said they had been alerted to the suspects because they were holding a man at gunpoint.
The man was freed and the suspects were arrested and their weapons seized.
The Mexican defence ministry said Mr Barrios Caporal had confessed to being second-in-command to Martin Omar Estrada Luna, the local leader of the Zetas drug cartel in San Fernando, where the murders happened.
Mr Barrios Caporal reportedly said they had stopped the Central and South American migrants "to find out if they belonged to the Gulf cartel".
The Zetas were originally the armed wing of the Gulf cartel.
But they split from their former allies and have since become bitter rivals fighting for control of the drug smuggling routes to the United States.
The Mexican defence ministry has described the Zetas as "the most formidable death squad to have worked for organised crime in Mexican history".
Analysts say the Zetas have switched their operations from the west coast state of Michoacan to Tamaulipas on the east coast, and down to Cancun in the Yucutan Peninsula.
As the Zetas have tried to take over territory controlled by other gangs, there has been a sharp increase in murders of rival gang members.