Solomon Makgale, a South African police spokesman, today said that the Hawks, a national investigative unit of the police, was handling the case.
The South African Revenue Service, the national tax-collecting authority, says customs officials seized the money on September 5 because it was over the legal limit for bringing cash into the country.
Travellers arriving in South Africa with more than USD 2,300 are subject to stringent checks.
The City Press newspaper says the cash was in unused USD 100 bills and was packed in three suitcases aboard a private jet that had come from Abuja, the Nigerian capital.