South African police say they arrested a 28-year-old man in connection with a bomb threat and what was suspected to be two anthrax powder scares at the Johannesburg headquarters of the country's national roads agency Sanral.

Police spokesman Captain Paul Ramaloko said the man, who will face charges relating to acts of terrorism, was arrested by the organized crime unit, the Hawks, at Sanral's operations center on Wednesday afternoon.

Ramaloko said that on three occasions recently, Sanral employees were evacuated from the (Johannesburg) center as a result of threats. Police seized white powder that some feared was anthrax, but testing proved it was not.

Sanral spokesman Vusi Mona said the suspect was employed by a service provider in the Sanral building.