Bomb disposal experts and counter-terrorism officers were scrambled to the motorway near Lichfield after a passenger on the Megabus service from Preston to London reported seeing vapour coming from a man's bag at around 8am.
The 48 passengers, including at least one young boy, were led from the coach and walked about 300 yards to a cordoned-off area on a closed carriageway. Witnesses described how they came off the coach "one by one holding their arms up" to prove they were not armed. They were then surrounded by officers and searched.
Initial reports suggested that a passenger had been spotted pouring liquid into a bag, which was giving off fumes. Officers trained for chemical, biological and nuclear attacks were sent to the site and decontamination units were set up as part of the pre-prepared response to a major incident.
The closure caused long tailbacks and delays, with both carriageways closed for more than four hours. Nick Jones, who was stopped on the motorway for more than an hour and a half, said that police warned him to stay in his car, keep his windows closed and not to use air conditioning. "I was beginning to feel a little uneasy," he told the BBC. "I was beginning to look around for an escape route."
Police later confirmed there was no terror threat. "The information received concerned a report of vapour escaping from a bag which on investigation turned out to be a health improvement aid for smokers," said a Staffordshire Police spokeswoman.
"We can now confirm that, whilst this was a genuine security alert, the significant concerns reported to us were unfounded."
The operation was mounted amid heightened concerns of a terrorist attack in the run-up to the Olympics and Paralympics.
Armed Response Unit: Marksmen arrive in an Audi A6. Inside, a locker holds firearms – from Heckler & Koch pistols to Tasers. Propped against a marked vehicle is a bullet-proof shield.
Decontamination tent: Part of the Incident Response Unit, this shower tent is used to clear contaminants. Each one can process 150 people an hour and each unit carries two facilities.
Incident Response Units: Designed for chemical, biological or nuclear attacks, these trucks carry yellow crates, unloaded with a forklift, containing decontamination equipment.
Passenger pen:
Standard protocol meant that passengers had to walk slowly and individually from the bus while surrounded by armed officers, then sit in rows in a taped-off square.
Royal Logistic Corps Bomb Disposal truck: These carry remote-controlled robots used to probe suspicious packages. The "Bomb Disposal" signs can be taken off so as not to cause alarm.
Major incident response: The phone call from the coach driver led to at least two police forces, two fire brigades and a military unit being involved – an estimated 200 personnel.
