Education Minister Kader Asmal has arrived at Wits University where a suspended student took a female member of staff hostage on Wednesday in an apparent bid to be readmitted.
Asmal had been briefed on the situation and might be asked to negotiate with the student in a bid to end the stand-off, Captain Schalk Bornman said at the scene.
The student took the woman hostage on Wednesday morning in an office in the senate building on the campus in central Johannesburg. The man had apparently tied his hostage's hands with a computer cable but it was not yet known if he had hurt her, Bornman said.
The student is believed to have a gun.
Task force policemen have been deployed inside the building.
Telephone lines have been opened to allow the negotiators to communicate with the student, Bornman said.
The area around the building has been closed to the public. - Sapa