A TINY BUT dangerously radioactive capsule, which fell off a truck along a remote stretch of desert highway in Western Australia last month, was found today, authorities said.

“It’s a good result, as I’ve said it’s certainly a needle in a haystack that has been found, and I think West Australians can sleep better tonight,” West Australian emergency services minister Stephen Dawson told reporters.

Authorities scoured hundreds of kilometres of highway in search of the tiny capsule.

It was discovered at the side of a desert highway just south of the town of Newman — near the Outback mine it was transported from, the state’s emergency services commissioner Darren Klemm said.

The six-day hunt came to an end after a search vehicle detected radiation while travelling along the highway, with authorities now working to safely remove the capsule before taking it to a secure location, Klemm said.

The solid, silver-coloured cylinder is smaller than a human fingernail — just eight millimetres by six millimetres — but the authorities say it contains enough Caesium-137 to cause acute radiation sickness.

It disappeared from a truck that drove to the suburbs of Perth from a remote mine 1,400 kilometres (870 miles) north of the state capital — farther than the distance from Paris to Madrid.

Portable radiation monitors that can be mounted on vehicles were used to detect radioactive emissions across a 20-metre radius along the route, Western Australia’s emergency services said.

Mining giant Rio Tinto apologised for losing the capsule.

“We recognise this is clearly very concerning and are sorry for the alarm it has caused in the Western Australian community,” said Rio Tinto Iron Ore chief executive Simon Trott in a statement sent to AFP.

“We have launched our own investigation to understand how the capsule was lost in transit,” he added.

The radioactive capsule, part of a gauge used in the mining industry to measure the density of iron ore, was transported by a certified Rio Tinto contractor, he said.