The guard, named as Kenny Finlayson, 38, is understood to have worked at the prison for a number of years. He has been suspended by prison bosses pending an investigation into the find.
They said: “A report will go to the procurator fiscal.”
The prison is run by private firm Sodexo, and a spokesman said: “We can confirm a member of staff has been arrested.
"It would be inappropriate to comment further while a police investigation is underway.”
READ MORE: Killers go on violent rampage with makeshift weapons at HMP AddiewellA source quoted by The Sun newspaper said: “Phones are a real problem in the jail.
"Kenny had only returned to work for a few days after being off for a spell.
“He was recently promoted to a senior officer position.”