A baby-trafficking ring aiming to pass infants on for adoption had operated for more than 20 years in Mexico and sent children to Italy as well as Ireland, according to a Mexican official.
Authorities have detained nine suspects and interviewed 15 Irish nationals in the past week in western Mexico in a probe into the trafficking network. Ten babies have also been taken into custody.
Documents seized from a lawyer's office during the probe showed children had been "legalized" by the network in cases dating back to 1990, said Blanca Barron, an official from the Jalisco state attorney general's office.
Birth certificates, adoption papers and receipts sent to the babies' natural mothers were among the discoveries.
Some children had been sent to Italy as well as Ireland, Barron said, but she was unable to say how many youngsters had been victims.
Suspects from the law firm were missing, she said.
Nine people, two men and seven women, have been detained in the past week, including a 21-year-old woman who was denounced by her family when she tried to negotiate the sale of her two sons, sparking the investigation.
Four of the children taken into custody showed signs of sexual abuse, prosecutors said.
Fifteen Irish nationals have been questioned but none were charged. It is unclear if they knew about the illegality of the process.
The network, which apparently operated through small advertisements in the local press, paid 1,200 pesos (88 dollars) per week to mothers during their pregnancies and provided medical aid.