Police Brig. Hangwani Mulaudzi said Tuesday that there were "rumors" that the cash was headed for the Islamic State group but that authorities had so far not found any "tangible evidence."
Islamic State extremists control parts of Syria and Iraq and have welcomed thousands of foreign fighters into their ranks.
South African tax authorities say five passengers carrying the cash were detained while boarded an Emirates flight at Johannesburg's main international airport on Aug. 28.
