AN unmarked box of shotguns has made its way through tight security and into the loading area of one of Adelaide’s prisons.

The box of eight shotguns was delivered to Adelaide Women’s Prison on Monday by mistake.

Entering through tight security in the back of a courier’s truck, the shotguns were only discovered when the boxes were being unloaded by Correctional Service Department personnel in an area reported to be frequented by prisoners.

The department said there was no ammunition with the firearms, which were destined for the Operations Security Unit, which is next door to the prison.

The prison was locked down following the discovery and the weapons safely removed by Operations Security Unit officers.

A department spokesman said an investigation would focus on how the guns were delivered to the wrong address on the same road.

“Prison staff received the delivery in accordance with the prison operating procedures and it was under the direct escort and supervision of custodial staff at all times,” the spokesman said.

“The delivery was then directed to its permanent housing facility.

“In accordance with legislation, no ammunition was included with the delivery and the safety and security of the prison was not compromised.”

Public Service Association general secretary Neville Kitchen said the union would be conducting its own investigation.

“I am yet to get confirmation of exactly what happened, but the PSA is concerned about any security breach at the state’s prisons,” Mr Kitchen said.

“A breach of this variety is extremely concerning.

“I believe the Department of Correctional Services is already conducting an investigation.

“Then the PSA will begin an investigation to ensure breaches like this don’t happen again in the future.

“This is one of the most serious security breaches possible at a prison.

“Any firearms in or near of prison certainly present a danger not only to our officers, but to prisoners as well.”