A terror alert aboard on Megabus which closed the M6 toll on Thursday was caused by a "health improvement aid for smokers", police said.
Armed officers responded to a genuine security alert from a concerned member of the public on board the coach travelling from Preston to London, Staffordshire Police said.
"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," a force spokeswoman said.
SCROLL DOWN TO SEE THE DRAMATIC POLICE RESPONSE TO THE 'SMOKER'S AID'
The four-and-a-half hour terror scare on the M6 toll road has ended with no suspects and no one hurt.
People began to speculate on what could have caused the incident after scores of police and a bomb disposal unit descended on a Megabus carrying 48 passengers on Thursday morning.
A report from the scene suggested a man was seen pouring liquid into a smoking bag on board the coach but police said it was not a chemical incident.
Staffordshire Police said the incident, which saw passengers evacuated from the coach and searched, was not a counter-terrorism operation after speculation officers were dealing with a possible chemical attack. Police said there were no suspects and no danger to passengers.
"Following an initial assessment, we can confirm that no-one has been injured and that there is no danger to passengers at the scene or any other travellers who were on the motorway at that time. We are also not treating anyone as a suspect."
As the danger subsided, Twitter users began posting what they thought had caused the chaos, from pot noodles to cup-a-soups.
The M6 toll road was closed and scores of police and emergency workers attended the incident
Witness Nick Jones, who was stopped on the motorway for more than an hour and a half, told BBC News that police warned him to stay in his car, keep his windows closed and not to use air conditioning.
A spokeswoman for Megabus, which is operated by Stagecoach, said: "We are assisting police with their inquiries into an allegation made against a passenger who was travelling on board one of our services."