This certainly isn’t the first time this has happened in Mexico, and certainly won’t be the last.
See the following articles for further information on other previous incidents:
Border Battle: TX agents now looking for terrorists smuggling radioactive material
The strange trend of Mexican thieves stealing radioactive material by accident

Nine states were placed on high alert following the theft [Google]
THE MEXICAN government has placed nine states on high alert after radioactive material capable of creating a dirty bomb was stolen near the nation’s second largest city.
The Iridium 192, a potentially highly unstable material used in radiography equipment, was stolen on the outskirts of tourist hotspot Guadalajara.
Luis Felipe Puente, head of national emergency services, placed nine states on high alert after the material disappeared just half a day’s drive from the Texan border. Continue reading