Six people tested for possible radiation exposure have been released from a Mexican hospital, but are in custody suspected of stealing a lorry carrying highly radioactive cobalt-60.
Of the detained men, aged between 16 and 38, only the teenager showed signs of radiation exposure and was in good health, a spokeswoman for Hidalgo state's health department said.
The six were taken to the general hospital in Pachuca for testing and a fter being cleared were turned over to authorities in connection with the gunpoint theft of the lorry outside Mexico City on Monday. The cobalt-60 it was carrying was from obsolete hospital radiotherapy equipment.
Hidalgo health minister Pedro Luis Noble said earlier that the men suffered from skin irritations and dizziness, but none was in a serious condition. Only one was vomiting, a sign of radiation poisoning.
The theft triggered alerts in six Mexican states and Mexico City, as well as international notifications to the US and the International Atomic Energy Agency in Vienna. It raised concerns that the material could have been stolen to make a dirty bomb, a conventional explosive that disseminates radioactive material.
The atomic energy agency said the cobalt has an activity of 3,000 curies, 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".
But Mexican authorities said the thieves seemed to have targeted the lorry, which has a moveable platform and crane, and probably did not know about the dangerous cargo.
The lorry driver stopped to rest at a petrol station when two armed men made him get out, tied his hands and feet and left him nearby. The lorry was found abandoned on 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 half a mile from the truck in an empty rural field, where authorities said they were a risk only to those who had handled them and not to anyone in Hueypoxtla, the closest town of about 4,000 people. There was no evacuation.
The pellets were from a hospital in the northern city of Tijuana and was being transported to nuclear waste dump in the state of Mexico, which borders Mexico City.
Authorities maintained a 500-yard cordon around the site where the cobalt-60 still remains in the state of Mexico and were continuing to extract it safely, said Juan Eibenschutz, director general of Mexico's National Commission of Nuclear Safety and Safeguards.
"It's quite an operation and it is in the process of being planned," he said. "It's highly radioactive, so you cannot just go over and pick it up. It's going to take a while to pick it up."