The process is not always simple for young immigrants in the United States who don't have birth certificates or passports handy, said Abigail Calleja, consul for protection at the Mexican consulate in Atlanta.

CNN: Young immigrants prepare for new U.S. deportation policy

The Mexican authorities have arrested several other people who they accuse of being connected to the consulate killings.

CNN: STORY HIGHLIGHTS

Lesley Enriquez - a US citizen working at the Juarez consulate - her American husband, Arthur Redelfs, and Jorge Alberto Salcido, the Mexican husband of another consular employee, were shot dead in two separate incidents on 13 March in the border city of Ciudad Juarez.

BBC: Clinton pledges broader US effort on Mexico drugs gangs