PERTH, Australia — A mining corporation on Sunday apologized for losing a highly radioactive capsule over a 1,400-kilometer (870-mile) stretch of Western Australia, as authorities combed parts of the road looking for the tiny but dangerous substance.

The capsule was part of a device believed to have fallen off a truck while being transported between a desert mine site and the city of Perth on Jan. 10.

The truck transporting the capsule arrived at a Perth depot on Jan. 16. Emergency services were notified of the missing capsule on Jan. 25.

Western Australia emergency services have called on other Australian states and the federal government for support finding the capsule as they lack equipment. The capsule measures 8 millimeters by 6 millimeters (0.31 inches by 0.24 inches), and people have been warned it could have unknowingly become lodged in their car’s tires.

The caesium 137 ceramic source, commonly used in radiation gauges, emits dangerous amounts of radiation, equivalent of receiving 10 X-rays in an hour. It could cause skin burns and prolonged exposure could cause cancer.

The chief executive of the mining giant Rio Tinto Iron Ore, Simon Trott, said the company was taking the incident very seriously and apologized for causing public concern.

“We recognize this is clearly very concerning and are sorry for the alarm it has caused in the Western Australian community,” Trott said. “As well as fully supporting the relevant authorities, we have launched our own investigation to understand how the capsule was lost in transit.”

The search has involved people scanning for radiation levels from the device along roads used by the trucks, with authorities indicating the entire 1,400-kilometer (870-mile) route might have to be searched.

Western Australia’s Department of Fire and Emergency Services publicly announced the capsule had gone missing on Friday, two days after they were notified by Rio Tinto.

Trott said the contractor was qualified to transport the device and it had been confirmed being on board the truck by a Geiger counter prior to leaving the mine.

Police determined the incident to be an accident and no criminal charges are likely.