Johannesburg - Czech businessman Radovan Krejcir declined to comment on Wednesday after a blast killed two people at his business in Bedfordview.
“Sorry, I'm not talking to the press,” he told Sapa by cellphone.
Police were still combing the scene of the blast that also left five people injured.
The device went off late on Tuesday afternoon at Krejcir's Money Point gold and diamond exchange office next to Johannesburg's Eastgate shopping centre.
Police helicopters landed at the scene on Wednesday morning.
Forensic experts told Sapa late on Tuesday evening that the building's roof had collapsed due to the magnitude of the blast.
A forensic expert, speaking on condition of anonymity, said they were still trying to establish what kind of explosive was used. - Sapa