Parts of Western Australia were under a radiation alert on Saturday after authorities said a radioactive capsule used in mining was lost en-route to the state’s capital, Perth.

Authorities in Australia’s largest state issued the alert on Friday for a “radioactive substance risk” in several regions, including Perth.

The small, silver capsule containing Caesium-137 got lost during transport from north of Newman – a small town in the remote Kimberley region – to the northeast suburbs of Perth, the Department of Fire and Emergency Services said.

“The substance is used within gauges in mining operations. Exposure to this substance could cause radiation burns or radiation sickness,” the agency said.

The capsule went missing while being driven in a truck from a mine to a Perth storage facility, the state’s health agency said. Newman is about 1,200 km (750 miles) northeast of Perth.

The truck left the site on Jan. 12 but the capsule was not discovered missing until this week, which was when emergency services were alerted, according to authorities.

The capsule was reportedly from a Rio Tinto Ltd (RIO.AX) mine. The company did not immediately respond to a request for comment.

Western Australia chief health officer Andrew Robertson said the capsule, if kept close to the body, could cause skin redness and radiation burns.

“If it was kept long enough and they were exposed for long enough they could have some more acute effects, including impacts on their immune system,” he told reporters.

It was thought at the vibration of the truck caused the gauge to fall apart and the item then came out of it, he said.