The M1 remains closed in both directions after a “suspicious object” was found underneath a bridge.

Motorists have been stranded for hours on the 11 mile (18km) stretch between junctions 15 at Northampton and 14 at Milton Keynes.

A bomb disposal unit was earlier seen travelling along the hard shoulder towards the scene. The Ministry of Defence confirmed it had provided police with “explosive ordnance device assistance”.

Highways England has posted diversions but it is unclear when the road will reopen.

Trapped northbound traffic is being cleared by funnelling motorists through Newport Pagnell services. National Express has added 45 minutes to travel times for services that use the motorway.

The object was discovered beneath a bridge at about 07:30 BST, Thames Valley Police said.

Ruth Middleton has been stuck in traffic for more than five hours. “I have got my laptop out, some people have been having naps. There hasn’t been a lot to do other than kill time,” she said.

On Twitter, one motorist wrote: “When you see a helicopter above you and kinda wish they were lowering a portaloo #m1 3 hours and counting…”

Another added: “Just heard a bang. Suspicious package dealt with maybe?”

Some people are playing football on the empty stretch of motorway. “Spirits high – waiting it out,” Liz Searle wrote.