RADIATION ... 6 admitted to hospital in Mexico... now suspects...the men were turned over to federal authorities in connection with the case of the cargo truck stolen Monday at gunpoint outside Mexico City. The cobalt-60 it was carrying was from obsolete radiation therapy equipment.

 Six people admitted to a hospital in central Mexico for radiation testing are suspects in the theft of a truck containing potentially deadly cobalt-60, a government official said Friday.

 Of the detained men, ages 16 to 38, only the 16-year-old showed signs of radiation exposure and he was in good health, a spokeswoman for Hidalgo's Health Department said on condition of anonymity because she isn't allowed to discuss the case.

 The six were detained Thursday as part of the investigation and taken to the general hospital in Pachuca for testing.

 After being cleared by health authorities on Friday, the men were turned over to federal authorities in connection with the case of the cargo truck stolen Monday at gunpoint outside Mexico City. The cobalt-60 it was carrying was from obsolete radiation therapy equipment.

 Officials have not said what roles the six allegedly had in the theft.

 The theft triggered alerts in six Mexican states and Mexico City, as well as international notifications to the U.S. and the International Atomic Energy Agency in Vienna.

 Authorities warned that whoever removed the radioactive material by hand was probably contaminated and could soon die, according to a Sky News report.

 The International Atomic Energy Agency said the cobalt has an activity of 3,000 curries, or Category 1, meaning "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."

 "What I was told (Thursday) is that there might be two people with severe radiation syndrome, but I do not have confirmation," said Juan Eibenschutz, director general of Mexico's National Commission of Nuclear Safety and Safeguards.

 The incident raised concerns that the material could have been stolen to make a dirty bomb, a conventional explosive that disseminates radioactive material. But Mexican officials said that the thieves seemed to have targeted the cargo truck with a moveable platform and crane, and likely didn't know about the dangerous cargo.

 The truck was found abandoned Wednesday about 24 miles from where it was stolen, and the container for the radioactive material was found opened. The cobalt-60 pellets were left about a half mile from the truck in an empty rural field, where authorities said they were a risk only to anyone who had handled them and not the surrounding population.

 The material was from obsolete radiation therapy equipment at a hospital in the northern city of Tijuana and was being transported to nuclear waste facility in the state of Mexico, which borders Mexico City.

 Eibenschutz said authorities continued to work on Friday at the site in Mexico state where the material was found to extract it safely.

 The Associated Press contributed to this report