By Miguel Gutierrez
MEXICO CITY (Reuters) - Six men suspected of stealing a dangerous radioactive cargo from a truck outside Mexico City earlier this week have been treated in a hospital for signs of radiation exposure and remain under police guard, officials said on Friday.
On Monday, thieves hijacked the truck that had been carrying cobalt-60, a radioactive substance used for medical and industrial applications that can also be used as an ingredient in a "dirty bomb."
Police located the truck on Wednesday but found that the robbers had removed the radioactive material from a protective case, exposing themselves to dangerous levels of radiation, before dumping it less than a mile away.
"The six people ... are presumed to be responsible or linked to the theft of the vehicle which was carrying the cobalt-60," said a government official, who asked not to be identified. He said the men remained in police custody.
Pedro Noble, the health secretary of the state of Hidalgo, told local television the men showed signs of "critical, close contact" with radioactive material. The state health authority later said the men, aged between 16 and 38, had been discharged after treatment.
The truck, which was taking the material from a hospital in the northern city of Tijuana to a radioactive waste-storage center, was seized when its driver stopped at a gas station in the town of Temascalapa, 35 km (22 miles) northeast of Mexico City.
Cobalt-60, the most common radioactive isotope of the metal, is also used for industrial radiography to detect structural flaws in metal parts, according to the U.S. Environmental Protection Agency.
Exposure to gamma radiation from cobalt-60 results in an increased risk of cancer, the EPA says.
(Reporting by Miguel Gutierrez; Additional reporting by Alexandra Alper and Luis Rojas; Editing by Gabriel Stargardter, Simon Gardner and Eric Beech)