Mexican officials seek thieves, likely sick from radiation MEXICO CITY -- Authorities sought at least two thieves on Thursday who had seized a truck with radioactive material in central Mexico, while a family who found and took home the exposed stolen container was under medical observation, officials said. The truck was hijacked Monday by gunmen who intercepted it north of Mexico City. It was transporting a large amount of highly active cobalt-60, a radioactive substance used in the treatment of cancer, from a hospital in Tijuana to a nuclear waste storage dump near the capital. The substance can be used in the making of dirty bombs, a fact that raised alarm here and abroad, especially given the presence in Mexico of violent drug trafficking and extortion gangs who might be eager to get their hands on such a valuable product. With a six-state search underway, the thieves apparently abandoned the truck north of Mexico City on Wednesday but made off with the lead box containing the radioactive material. For unknown reasons, they ditched it in a field about half a mile away after removing it from its protective shielding. Five members of a family, whose name has not been released, stumbled across the material, took it home and then, realizing what it was, called police, officials said. "They said they found the material in a vacant lot and took it home, thinking it was scrap metal that they could sell," said Julio Cesar Abreu, head of civil protection in the town where the container was found, Hueypoxtla. They are undergoing medical examinations, and some have been allowed to go home. Mexican authorities have secured the site, with the army and police cordoning off a large section including the spot where the material was found and the family's home. Officials are plotting the safest way to recover the material. The United Nations" International Atomic Energy Agency described the cargo as extremely dangerous. "It would probably be fatal to be close to this amount of unshielded radioactive material for a period in the range of a few minutes to an hour," the organization said in a statement Thursday. The head of Mexico's National Commission on Nuclear Safety and Safeguards was even more direct. The thieves who handled the material "are dead or are about to die," said Juan Eibenschutz. The international agency added that there were no indications that the cobalt-60 had been damaged or broken up and that there was "no sign of contamination to the area." In Washington, President Obama's spokesman, Jay Carney, said officials there did not believe the incident posed a threat to the U.S. Mexico has a poor track record of the handling this type of perilous waste. In the state of Chihuahua in 1983, radioactive waste was used in several tons of metal rods that went into the construction of more than 17,000 buildings and homes. The nuclear waste dump where the purloined truck was headed in Mexico state is surrounded by residential areas, where people have been complaining about health problems for years. American teacher is shot and killed in Libya Airline passengers at front lines of dispute over China air zone Toronto mayor: Bad boy Rob Ford puts Canada in global spotlight