LONDON (AP) — False alarm: British police said Thursday that reports of suspicious activity on a bus, which set off a massive emergency response and forced the closure of a section of a major highway in central England, were unfounded.

The "culprit"? An electronic cigarette.

Armed police evacuated passengers from the bus and bomb disposal units, ambulances and fire engines descended on the Weeford toll plaza of the M6 highway in the West Midlands, 116 miles (187 kilometers) north of London, after the initial reports Thursday.

The sweeping emergency response came just weeks before the July 27-Aug. 12 Olympics are due to be held in the British capital.

But several hours later, Staffordshire police said that the scene was safe and no suspects were in custody.

The force said it had received a "genuine report" from a member of the public about vapor escaping from a bag on the bus, which upon investigation turned out to be a an electronic cigarette — a device that aims to help smokers quit.

"We can now confirm that, whilst this was a genuine security alert, the significant concerns reported to us were unfounded," the force said.

It apologized for any inconvenience caused by the security response, saying it hopes people understand its duty to ensure public safety.