No South African citizens were on the Malaysia Airlines jet which vanished with 239 people on board, the international relations department said on Sunday.
Spokesperson Nelson Kgwete said the list of passengers released by the Malaysian carrier did not include South Africans.
"Our mission [in Malaysia] would have told us if there were any South Africans. There are no reports of South African citizens having been on that plane," said Kgwete.
He said there had been no suggestions that the four passengers who reportedly had questionable identities were South African.
Mystery surrounded the identity of two passengers who appear to have used stolen European Union passports to board the plane.
More than 30 hours after air traffic control lost communication with the Boeing 777, concerns were mounting over a possible security breach, as authorities in Southeast Asia said there was still no sign of the plane after the search resumed at sea.
Flight MH370 disappeared about an hour after leaving Kuala Lumpur en route to the Chinese capital.
On Sunday, reports by Agence France-Presse and Associated Press indicated that Malaysian authorities were also investigating the identities of at least two other passengers on the flight, in addition to the two who were found to be using stolen passports.
Malaysian Transport Minister Hishammuddin Hussein reportedly said they were now looking at four possible cases of suspect identities. He said Malaysian intelligence agencies were in contact with their international counterparts, including the FBI.
Malaysia Airlines said people from 14 nationalities were among the 227 passengers, including at least 152 Chinese, 38 Malaysians, 12 Indonesians, six Australians and three Americans. It also said a Chinese infant and an American infant were on board. – Sapa