PERTH, Australia — Authorities in Western Australia on Wednesday recovered a tiny but dangerous radioactive capsule that fell off a truck while being transported along a 1,400-kilometer (870-mile) highway last month in what an official said was like finding the needle in the haystack.

Officials said the capsule the size of a pea was found south of Newman on the Great Northern Highway. It was detected by a search vehicle travelling at 70 kilometers (43 miles) per hour when specialist equipment picked up radiation emitting from the capsule.

Portable search equipment was then used to locate it 2 meters (6.5 feet) from the side of the road.

“This is an extraordinary result … they have quite literally found the needle in the haystack,” said Emergency Services Minister Stephen Dawson.

Chief Health Officer Andy Robertson said the capsule did not appear to have moved and no injuries had been reported.

It contains the caesium 137 ceramic source, commonly used in radiation gauges, which 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.

Search crews had spent six days scouring the entire length of the highway.

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.

A government investigation has been launched into how the capsule fell off the truck and a report will be provided to the health minister.

Defence officials were verifying the identification of the capsule, which has been placed into a lead container for safety. It will be stored in a secure location in Newman before being transported to a health facility in the city of Perth.

The capsule got lost while being transported between a desert mine site and 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.

The chief executive of the mining giant Rio Tinto Iron Ore, Simon Trott, has apologized for the incident.