I apologize that my “mental map” of Mexico is so poor, but thought you might be interested in this, also posted on FR:
“Mexican authorities have issued an alert for five states after the theft of potentially dangerous radioactive materials.
A container of Iridium-192 used for industrial radiography was taken from a truck in the town of Cardenas in Tabasco state.
The states of Campeche, Chiapas, Oaxaca and Veracruz are also on alert.
Mexico’s civil protection agency says that the material can cause death within hours or days if mishandled.”
http://www.bbc.com/news/world-latin-america-32332271
Those places are more south. A lot of this occurs in Mexico, old medical sources stolen to sell as scrap, and well logging equipment stolen off work trucks.