Rio Tinto will launch its own investigation into how a highly radioactive piece of equipment went missing somewhere over a 1400-kilometre stretch of Western Australia.

It comes as authorities also launch their own probe and begin to comb parts of the roads for the capsule, which is smaller than a 10 cent piece, between the WA desert mine site and Perth.

The capsule is understood to have fallen from a truck of a contractor hired to transport the device after leaving the site in Newman, in the Pilbara, on January 10.

Rio Tinto Iron Ore chief executive Simon Trott said the company was taking the incident “very seriously”.

“We recognise this is clearly very concerning and are sorry for the alarm it has caused in the Western Australian community,” Mr Trott said on Sunday.

“As well as fully supporting the relevant authorities, we have launched our own investigation to understand how the capsule was lost in transit.”

WA emergency services have called on other states and the federal government for support finding the capsule as they lack the equipment to search for the device.

The search has involved people scanning for radiation levels from the device along roads used by the trucks, with authorities flagging the entire 1400-kilometre route might have to be searched.

Mr Trott said the mining giant was offering its full support to authorities and had done radiological surveys across the mine site and connecting access road.

WA’s Department of Fire and Emergency Services publicly announced the capsule had gone missing on Friday.

The silver 8mm by 6mm capsule is a Caesium 137 ceramic source commonly used in radiation gauges.

It emits dangerous amounts of radiation, which is the equivalent of receiving 10 X-rays in an hour.

It could cause skin burns and prolonged exposure could cause cancer. People have been warned it could have unknowingly become lodged in their car’s tyres.

It is suspected vibrations worked loose a bolt in the device the capsule was part of and the capsule then fell through that bolt hole.

The truck transporting the capsule arrived at a Perth depot in Malaga on January 16.

Mr Trott said the contractor was qualified to transport the device and it had been confirmed being on board the truck by a Geiger counter prior to leaving the mine.

Emergency services were notified of the missing capsule on January 25.

Police determined the incident to be an accident and no criminal charges are likely.

-AAP