Wardens at Durban's Westville Prison conducted a raid after a tip-off that dangerous weapons and an explosive device had been smuggled into the facility.
A source close to the prison said police and prison officials had responded to the tip-off and searched the prison.
Department of Correctional Services spokesman Logan Maistry confirmed that the law enforcement officials were currently conducting an "operation" at the prison.
"We routinely conduct such operations at facilities in the interests of safety of those in our custody. We are unable to provide further details of the operation at this stage."
SAPS spokesman Captain Nqobile Gwala said she wasn't aware of the raid and referred queries to the department of correctional services.