The search for the container and the truck in which it was located continues, Juan Eibenschutz, director general of the National Nuclear Safety Commission, said.
Officials think the thieves probable did not know they were stealing radioactive material when thet robbed the truck in Cardenas. The material presents no danger to the population as long as the source remains in the protective box.
Similar thefts have occurred three times since 2013. The material has always been recovered and no deaths have been reported.