Australian authorities are searching for a missing radioactive capsule containing Caesium-137, which fell off a truck during a 870-mile journey from Gudai-Darri mine site to Perth. The capsule is part of a gauge used to measure the density of iron ore feed and is emitting both gamma and beta rays. A team with specialized car-mounted and portable detection equipment has been sent to search for the capsule, but so far it has not been located, triggering a radiation alert for large parts of Western Australia. Rio Tinto has apologized for the incident and is supporting the search.