Mexico placed its capital and 10 states on alert after thieves stole a vehicle with a container full of radioactive materials. A private company employee left it in the back of his pickup truck.

“If you see the container, don’t open it,” the head of the nation’s civil protection agency Luis Felipe Puente tweeted on Sunday as he announced the alert. The agency, tasked with securing the public’s well-being, reported that the stolen substance presents a “low risk” but can cause cancer and other permanent health damage to any person who might try to open the container or be in contact with it “for a few hours.”

According to local media, the container belonged to a radiography company. It was made of stainless steel and displayed ‘radioactive hazard’ markings. The employee left the container on the back of his Nissan pickup truck in Mexico City’s Alvaro Obregon borough on July 6. When he noticed that the vehicle was missing, he contacted the authorities.

Mexico has already witnessed several cases of theft of radioactive materials in recent times. In February, thieves targeted a vehicle in the city of Leon, taking a nuclear densometer, a device used in geotechnical engineering to measure density. Two similar incidents occurred in 2017.