Authorities are scratching their heads after a piece of radioactive material went missing at a steel plant in South Australia.
The Environmental Protection Authority was called to the Liberty OneSteel site on the Eyre Peninsula three weeks ago with reports of a missing industrial bin level gauge - a measuring instrument containing a small radiation source.
Despite a combined effort of the Australian Radiation Protection and Nuclear Safety Agency, police, firefighters and steelworkers, the device - which is about the size of a domestic gas BBQ cylinder - is yet to be found.
The EPA said there was no risk to the public and the 35-year-old device had low levels of radioactivity.
"Based on its assessment of the incident and that the radioactive material has decayed to 100th of its original activity the EPA does not believe it poses a risk to workers or the public," a spokesperson said.
Plant owners GFG Alliance said the material was moved during maintenance works and there is no suggestion it has left the site.
The material is a few millimetres large and is being stored in a 50-kilogram drum.
Keith Baldry from the EPA told ABC Radio the material was likely thrown out.
"They're doing some decommissioning at the site and it's been likely incorporated into some of their waste piles, on that basis, we don't think there's a risk," Mr Baldry said.
A spokesman for ARPANSA said a team of experts with specialised detection equipment were performing "extensive radiological searches for the missing item".
He said repercussions would be determined by the regulator and the missing devices were not unusual.
"These devices do occasionally go missing both domestically and internationally due to a range of factors, including theft of vehicles," he said.
Similar gauges are common in large industrial sites across Australia, with 87 premises registered to hold sealed radiation sources in SA alone.
A missing and potentially deadly radioactive mining capsule sparked a widescale search when it fell off a Rio Tinto truck in the West Australian outback in January.
Search crews spent six days scouring a 1400km route amid warnings the caesium-137 in the capsule could cause radiation burns or sickness if handled, and potentially dangerous levels of radiation from prolonged exposure.
The capsule was eventually found two metres from the Great Northern Highway by specialist equipment designed to pick up emitted radiation.
An investigation by WA's Radiological Council concluded last month and found no charges or fines should be laid.
