Authorities in Mexico have detained six men suspected of stealing a truck earlier this week carrying medical equipment including a radioactive element.
The suspects had been admitted to a hospital in Hidalgo state with possible symptoms of radiation poisoning.
The truck was stolen on Monday as the driver made an overnight stop on the outskirts of Mexico City and was found abandoned two days later on a nearby field.
The Mexican authorities said the protective case containing the radioactive isotope Cobalt-60 had been tampered with.
Hospitals in the area had been told to look out for people with symptoms of radiation poisoning.
A health official said six men, aged from 16 to 38, had undergone tests at the General Hospital of Pachuca but none showed immediate signs of radiation poisoning.
They have been discharged by doctors but have been handed over to Mexican police.
