A corrections officer at Mobilong Prison has been arrested for possessing a prohibited item.

Police arrested the 42-year-old from Murray Bridge on Thursday after he was allegedly found in possession of the item just outside the prison.

They did not say what they had allegedly found.

Mobile phones, cigarettes, prescription drugs and alcohol are among the items people are not allowed to possess on prison grounds without a lawful excuse, according to Correctional Services regulations.

Police then searched the man's home, where they allegedly found a small amount of cannabis – for which he was fined – and seized a gun.

He was charged with firearms offences as well as for possession of the prohibited item.

It was the first time anyone had been charged under new rules about the buffer zones around prisons.

The law was changed on June 3 to include the offence of possession in a buffer zone: anywhere immediately around a prison, including in the car park.

The maximum penalty for the offence is five years in prison.

You can help keep local stories like this one free for everyone to read. Subscribe to Murray Bridge News today and support your independent, locally owned news service, plus get access to exclusive stories you won’t find anywhere else, for just $5.50 a month.