Chilean nuclear agency CCHEN said the stolen vehicle, a truck, was carrying a piece of industrial radiographic equipment called a SENTINEL 880, "which contains a radioactive substance Iridium-192."
Iridium-192 is a radioactive isotope of chemical element iridium, according to the U.S. National Center for Biotechnology Information. High doses of Iridium-192 are used to treat tumors. The substance is also used in clinical X-ray systems.
"Don't touch, manipulate or attempt to utilize the device, as it can cause serious health effects," CCHEN said in a statement.
The agency posted a photo of the equipment on its Twitter account and recommended anybody who spotted it or the stolen vehicle immediately call their local police or fire department.