Prisoners are gulping down mobile phones to hide the gizmos from guards.
Cons use the phones to keep their businesses going, or to place their orders for drugs.
But they risk death by swallowing the gadgets to keep them secret.
The must-have model is the 2in Zanaco Fly, which can change hands in jails for up to £1,000 because it is easier to consume.
The Sunday People can reveal the first official cases of phone swallowing happened at HMP Rochester, Kent.
A report out this week said lags gulped them down before a cell search at the category C jail.
Prison watchdog the Independent Monitoring Board said it was aware of “two cases where a mobile phone was swallowed by a prisoner”.
It added: “The small size of phones acts as an enabler to prisoners for procuring drugs.”
A source said: “People take all kinds of risks to keep a phone as they can use it to carry on running their criminal enterprises.”
Phone swallowing has lead to one medical emergency. Doctors operated on a lag in Dublin to remove a mobile before it killed him.
An article in the International Journal of Surgery Case Reports said chemical and electrical discharges from mobile batteries can cause vital organs to shut down.
The Ministry of Justice said it was “increasing searches and using specialist equipment” to stop mobiles getting into prison.
