Smalberger told the media that prisons usually have events in which they do for the prisoners, but condemned this one.
"At Johannesburg Prison there was an internal event organised for inmates to celebrate Youth Month‚" Gauteng correctional services spokesman Ofentse Morwane earlier told local media outlet Times Live.
The department said preliminary findings indicated 13 officials would be served with letters of contemplation of suspension, which means they would be questioned and, based on the outcome of questioning, face suspension.
"The explicit entertainment was a clear breach of security and this type of conduct is unacceptable", Mr Smalberger said.
"The images were taken during an event related to June 16, but this form of entertainment was not however approved", he said.More news: Capt (r) Safdar to JIT: Panama probe "modern 58(2b)"
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However, others were angry that the event had been allowed to go ahead.
He said the department condemns the incident with the contempt that it deserves. It will be led by a senior director in the correctional services outside of Johannesburg.
The department added there was a "clear" breach of security plans approved for the event, but some officials obviously chose to go against them.
Smalberger said the final report was scheduled for June 30 and he expects that more prison officials would be suspended.
Acting national commissioner James Smalberger says, "We will make sure that those found guilty face the consequences of their actions and also that sufficient measures are put in place to ensure that similar incidents do not repeat themselves".