THE A1 is now reopen after a number of unexploded detonators found in North Yorkshire were blown up by the army.
North Yorkshire Police and the Army have discovered a number of "ageing detonators", close to the A1 near Marne Barracks in Catterick.
A police spokeswoman said the detonators were moved by the Army's bomb disposal team to a safe area where a controlled explosion took place.
A section of the motorway was closed since this morning after an explosion was heard at about 3am, but the spokeswoman said the detonators were not the cause of the original explosion, but found by officers during searches to identify the blast site.
The spokeswoman said no injuries had been reported, and the closure of the A1 was "a precautionary measure while police conduct their enquiries", and confirmed the noise of an explosion was reported by staff at Marne Barracks, but an actual explosion site had not yet been located.
Superintendent Dave Hannan said police, the North East Counter Terrorism Unit, explosives detection dogs and the National Police Air Service and military personnel all took part in searches throughout the day.
However, Supt Hannan said the cause for the initial call remains a mystery, as no sign of an explosion had been found, but thanked the public and motorists for their patience after a six-mile stretch of the A1 was closed off.
He said: "In view of the location of the suspected explosion, the source of the information, the current threat to UK security and a report a few hours earlier of a vehicle seen in suspicious circumstances outside the barracks, we were not prepared to take any chances with peoples' safety and had to carry out a very extensive and thorough investigation.
"Officers have now worked throughout the night and day to identify and locate the driver of the vehicle and we are now satisfied that he was not connected to the reported explosion and we have now eliminated him from our enquiries. We thank the driver of the vehicle for his patience and cooperation. We have also ruled out any link to terrorism."
Supt Hannan said police "may never find out what the source of the explosion was", but were "satisfied that there is no threat to members of the public".
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