Australian authorities found a radioactive capsule smaller than a coin that was lost in the vast Outback. The radioactive capsule was part of a gauge used to measure the density of iron ore feed from Rio Tinto's Gudai-Darri mine in the state's remote Kimberley region.

Australian authorities on Wednesday found a radioactive capsule smaller than a coin that was lost in the vast Outback after nearly a week-long search along a 1,400 kilometres (870 miles) stretch of highway, officials said.

The Caesium-137 capsule was discovered when a vehicle travelling at 70 kms per hour equipped with specialist detection equipment picked up the radiation, according to officials from the state of Western Australia.

The search team then used portable detection equipment to find the capsule, which was located about 2 metres from the side of the road, they added.

"I do want to emphasise this is an extraordinary result," Western Australia's Emergency Services Minister Stephen Dawson said in a news conference.

"When you consider the scope of the research area, locating this object was a monumental challenge, the search groups have quite literally found the needle in the haystack," Dawson said.

The military was verifying the capsule and it would be taken to a secure facility in the city of Perth on Thursday, he added.

Officials from Western Australia's emergency response department, defence authorities, radiation specialists and others have been combing the a stretch of highway for the tiny capsule that was lost in transit more than two weeks ago.

The radioactive capsule was part of a gauge used to measure the density of iron ore feed from Rio Tinto's Gudai-Darri mine in the state's remote Kimberley region. The ore was being taken to a facility in the suburbs of Perth - a distance longer than the length of Great Britain.