Counter terror authorities are investigating following the discovery of a uranium shipment at Heathrow Airport.

The find immediately sparked fears the cargo was to be used as a component of a nuclear ‘dirty bomb’.

But one security expert believes the explanation may prove to be more mundane.

According to reports, the material was destined for Iranian nationals in the UK but originated from Pakistan. It arrived at terminal four on an Oman Air flight from Muscat, Oman.

The shipment arrived in Britain in the hold of a passenger jet and was picked up by specialist security scanners as it was transferred to a freight shed, triggering alarms.

Border Force agents isolated the unregistered shipment in a dedicated radioactive room. Counter terror police were alerted immediately.

Police are tracing an Iranian company’s UK premises where the material was due to be delivered.

No arrests have yet been made since the discovery on December 29 but British officials will be keen to thwart any notion of the material being used in a dirty bomb, a mixture of explosives and radioactive stimulants.

MORE UK SECURITY NEWS

According to a report in the Sun, a source told the newspaper: “There are real concerns over what the Iranians living here wanted with non-disclosed nuclear material.”

But Security Journal UK columnist Philip Ingram MBE said: “The greater likelihood is that this will turn out to be traces of uranium sent innocently, but without the proper paperwork, as a lab sample or something like that.

“What it does show is that the kit being employed at Heathrow is doing its job.”

According to the Sun, ex-commander of the UK’s nuclear defence regiment Hamish De Bretton-Gordon said: “For uranium to turn up on a commercial airliner from Pakistan to an Iranian address in the UK is very suspect.”

Forensics teams have spent days examining the package after it was picked up as it was moved to a freight shed owned by handling firm Swissport.