[Omah]

http://www.bbc.co.uk/news/uk-england...ngham-18719962

A police source told BBC Radio WM a passenger was seen pouring a liquid into a box, which then started smoking.

The motorway was closed in both directions between junctions T3 and T4 at Weeford Park Plaza, near Lichfield, at 08:20 BST.

Police said the Megabus coach carrying 48 passengers stopped on the hard shoulder "of its own accord".

A Megabus spokeswoman said the coach was heading south from Preston to London when it was stopped.

"We are assisting police with their inquiries into an allegation made against a passenger who was travelling on board one of our services," the firm's spokeswoman added.

Nick Jones, a sales manager from Cambridge, was caught up in the incident while driving to the Lake District.

He said he was about four vehicles behind the coach when police stopped traffic.

"I've never seen so many ambulances turning up, also armed police, helicopter and dozens of police cars.

"We were told to stay in our cars, keep windows up and not put air conditioning on.

"Police were looking in hedgerows and verges on the northbound carriageway.

"It all just took off, ambulances left right and centre and armed police in black caps."

The fire service, police from the West Midlands and Staffordshire forces and ambulance crews are at the scene.

The Highways Agency said the closure was likely to remain in place until early afternoon.

Diversions are in place and trapped traffic was being turned around, police said.