A stretch of motorway was closed as police swooped to investigate a bomb scare on a bus in Scotland – but the “suspicious item” turned out to be an e-cigarette.

Passengers travelling along the M77 near Glasgow were evacuated from the bus and made to stand on the hard shoulder in gales and torrential rain as Storm Desmond hit on Friday night.

The alert was stood down almost an hour later after officers discovered the innocent source of the scare.

Calum McGregor, who had raised the alarm, told STV: “My partner and I became aware of a passenger behaving suspiciously with a device in his lap.

Vapourisers need to be regularly re-wicked by users (Getty Images)

"I got up under the pretence of looking for the toilet and saw he appeared to be attaching pipe-cleaner wire to a large oblong battery.

“I alerted the driver of a possible bomb on board and asked him to quietly pull over and call the police.”

But the item turned out to be an e-cigarette being re-wicked by passenger Chris Barron, a musician on his way home to Ayr after seeing friends.

After eventually being allowed to continue his journey, he wrote about his shock over the incident on Facebook.

Mr Barron said he was “none the wiser” as to what caused the alert until police arrived and asked him to step behind the bus for questioning.

Part of the M77 motorway had to be shut as police investigated the alert (Getty Images)

“They asked me if I had any electronic devices at all, which I replied ‘yes’ to,” he wrote.

“I showed them my unfired freshly cottoned vape. They laughed and shook their heads.

“Told me I hadn’t done anything wrong so not to worry about it and apologised. Took my name and told everybody to get back on the bus.

“I’ll say for the record these officers were sound about the whole thing so kudos to them.

“When the police were asked why they took so long to arrive they answered…’We had to close the entire motorway’.”

Mr Barron, who was born in California but lives in Scotland, is a bassist in vocalist in ska-punk band The Hostiles.

He described himself as a “25-year-old white guy with a full beard” and said that although he was aware that some people might “think you’re a terrorist”, he is keeping his dark facial hair.

Mr McGregor accused him of causing “a lot of concern and fear...with no thought to what that looked like to others on the bus”.

But Mr Barron said that if he had been asked what he was doing, he would have “politely explained” that he was merely reworking his vapouriser and that there was no cause for concern.

“I guess the lesson to be learned here is…think before you vape!” he added.

A spokesperson for Police Scotland told the Independent their officers were called at shortly after 8.35pm about “a man acting suspiciously” on the bus at junction four of the M77.