Malaysia is hunting for a radioactive device which went missing from a pickup truck earlier this month.
Authorities say the radioactive substance inside the radiography device could spread dangerous contamination if dismantled improperly.
There are also fears it could be used as part of a weapon – a so-called dirty bomb – if it fell into the wrong hands.
Authorities have confirmed the device is missing but have insisted that “everything is under control”.
The missing object is used in industrial radiography – it belonged to a firm that does tests, calibrations and inspections for oil and gas companies and other heavy industry firms.
The 23kg (50lbs) large metal tube with a carrying handle had reportedly been used to spot cracks in metal.
It contains the radioactive isotope iridium-192 which can cause radiation exposure or be used as a weapon if combined with a conventional explosive device.
Whether or not the missing iridium can indeed be used for a so-called dirty bomb depends on how much of it was inside the device.
According to the International Atomic Energy Agency, iridium-192 can cause permanent injury if handled for minutes to hours, and could be fatal if in close proximity for hours or days.
The Inspector-General of police Mohamad Fuzi Harun said a similar incident happened last year and that there has been no information on that device either, the Bernama news agency reported.
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Police and local media have detailed how the device was being carried on the back of a truck in the capital, Kuala Lumpur.
It had been used at one site on the outskirts of the city and was then driven to another location.
Upon arrival, the drivers noticed the device was missing. The two men were taken in for questioning but have since been released.
There is speculation the device might either have been stolen or fallen off the pickup while driving.
A police official said an investigation had been launched without giving further details, local media reported.
Deputy Home Minister Azis Jamman confirmed the incident had taken place but insisted “everything is under control”.