A spokesman for the Highways Agency said the closure on the A1 in North Yorkshire is now expected to remain in place until between 5.30pm and 6pm.
Earlier today they had anticipated that the road would re-open at around 3pm.
Police are continuing the search for the source of an explosion reported by staff at the Marne Barracks, in Catterick, at 3am.
Police say they still haven't managed to locate the site of an explosion close to Marne Barracks in Catterick.
Staff at the Barracks reported hearing an explosion around 3am, but the search for where it happened has been hampered by darkness and poor weather.
The search remains focused on the area outside of the barracks and the area next to the A1 although police they can't rule out the possibility it happened within the boundary of the barracks.
The safety of members of the public, including passing motorists, is our prime concern and therefore all security precautions must be taken to protect members of the public until we find out exactly what has occurred.
Extraordinary images of an empty A1 at Catterick have been taken by ITV News Tyne Tees. On what is expected to be one of the busiest shopping days of the year, the A1 motorway is closed in both directions as police investigate reports of a possible explosion in the Catterick Garrison area.
The Highways Agency says it expects the A1 around Catterick garrison to remain closed until around 3pm.
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Police have closed the A1 in both directions in North Yorkshire after reports of a possible explosion in the Catterick Garrison area.
North Yorkshire Police say a report was received at 3am Saturday after an explosion was heard in the Catterick area. There are no reports of any injuries at this time.
Both slip roads to Catterick have also been closed and diversions have been put in place.
Motorists are advised to avoid the area at this time.
A police spokesman says this is a precautionary measure while police conduct their enquiries.
North Yorkshire Police have released this e-fit image of a man suspected of indecently exposing himself to two young girls.
The incidents happened in Bedale on Saturday 28th June and then separately in Catterick on Sunday 29th June.
In both cases the suspect was driving a black VW Polo, or similar car, and is described as being aged in his late forties or fifties, with dark hair which is greying and a tanned complexion.
Detective Inspector Shaun Page said: "If you do recognise him, I urge you to come forward and contact the police immediately.
“If someone is identified and they are not responsible we will be able to quickly eliminate them from our enquiries.”
Detectives in North Yorkshire said they had received two reports of indecent exposure to young girls, which may involve the same man.
In the latest incident, the driver of a black VW Polo stopped on Mowbray Road in Catterick at about 12:30pm and indecently exposed himself to a young girl. He was described as having black or dark brown hair and was wearing square shaped glasses.
In the earlier incident, a man matching a similar description pulled up in a black VW Polo or similar-looking car on Benkhill Drive in Bedale and performed a "lewd act" in front in a 10-year-old girl. It happened at about 3:30pm on Saturday.
Neither girl was injured but both are said to be upset.
Police said a man had indecently exposed himself to a 10-year-old girl, close to a school, in North Yorkshire.
The man allegedly stopped near the girl on Benkhill Drive, Bedale, in a black Volkswagen Polo or similar-looking car, performing a "lewd act".
He did not try to touch the victim and she was not injured, before the car pulled away towards Fitzallan Road.
Officers want to trace a man in his 50s, with a tanned and wrinkled complexion and short black, greying hair.
He was wearing rectangular silver framed glasses and possibly a short sleeved top.
It happened on Saturday, 28th June at about 3:30pm.
North Yorkshire Police said it was believed to be an isolated incident.
“Although the girl was not physically injured as a result of this incident, it has naturally left her very upset by the experience.
“If you are the driver of the car and there has been some kind of confusion, I urge you to come forward straight away so that officers can take a statement from you.
“I am also keen to speak to anyone who witnessed the incident, or can help to identify the man involved, and I ask them to contact the police as soon as possible.”