Wardens at a caught an inmate with a stash of zombie drug Spice worth about £20,000.
They discovered 40 pages of A4 paper had been laced with the powerful mind-altering stimulant inside the prisoner’s cell.
Each sheet is estimated to be worth about £500 – with postage stamp-sized pieces changing hands between offenders for £5.
Officers made the find at Glasgow’s HMP Barlinnie after acting on a tip-off on Friday.
The dramatic haul was made just 48 hours after officers at the top security prison had their cars set on fire inside the staff car park.
Insiders say scanners used by the Scottish Prison Service (SPS) to detect new psychoactive substances (NPS) can fail if the entire surface has been soaked in liquid, making it all the same colour.
A source said: “This was a major find for the prison staff.
“Spice has become a big problem among the inmates.
“Each sheet was worth £500 and a small piece costs just £5.
“That’s enough to send someone off their head.
“Staff found about 40 bits of paper. It would’ve been a nightmare for them had it been circulated around the prison.
“The scanners don’t always work and staff sometimes need to use their intuition.
“For example, if an inmate receives an A4 sheet of paper which contains just a couple of sentences of writing, there’s a very good chance it’s been laced with Spice.”
According to latest figures, NPS have been found on Scottish prisoners more than 520 times in the past nine months – triple the number seized three years ago.
There were 189 incidents at HMP Kilmarnock in Ayrshire – the highest in Scotland – 109 at Barlinnie and 46 at HMP Perth in Tayside.
Officials at Barlinnie gave prisoners tips on safe drug use days after an inmate’s suspected suicide last year from taking an NPS, formally known as “legal highs”.
An 11-point checklist circulated around the jail highlighted a “major concern” over the types of substances abused inside the halls and a lack of knowledge over what is contained inside them.
It was seen as an admission by the SPS that the use of Spice was rife within the prison.
NPS have been dubbed a zombie drug because of the condition in which it leaves users.
Last Wednesday night, Barlinnie officers had their vehicles damaged in a fire attack inside the staff car park.
An Audi and a Volvo parked close to the main entrance were burnt in the incident.
The source said: “It’s not believed that the staff who had their vehicles damaged were specifically targeted.
“It’s thought that it was an attack on prison employees and not them as individuals.”
The SPS said security measures included X-ray machines and body scanners. They confirmed officers had discovered NPS during a search.
But Police Scotland yesterday said they had not been informed of the discovery.
The prison said: “Anyone found in possession of contraband or attempting to smuggle such items into our prisons will be reported to the appropriate authorities.”
