The Anglo-Australian miner said it will investigate the incident thoroughly to ensure a situation of this sort does not repeat.
"As part of our investigation, we will be assessing whether our processes and protocols, including the use of specialist contractors to package and transport radioactive materials, are appropriate," Rio's Iron Ore Chief Executive Simon Trott said.
The search to find the capsule used to measure the density of iron ore feed from Rio's Gudai-Darri mine in the state's remote Kimberley region involved at least six government agencies including the Department of Defence, the police and the Australian Nuclear and Science Technology Organisation. (Reporting by Roushni Nair in Bengaluru; Editing by Krishna Chandra Eluri)