One person has died and at least 20 others sustained injuries when a plane crashed near Wonderboom Airport in Pretoria, South Africa, officials said. "Our medical services are currently on the scene. They've been treating the patients," Russel Meiring, a spokesperson for emergency service provider ER24, told Xinhua news agency. ER24 will move the treated patients to nearby hospitals, he said. Details of the cause of the crash on Tuesday are yet to be established, but authorities confirmed that the plane hit a factory building before crashing. South African news outlet ENCA quoted an eyewitness saying: "I just saw something dropping down from the sky, but I didn't know what it was, and the next thing I saw was an explosion and a big bang." The charted aircraft, Convair 340, belongs to the Dutch airline Martinair. It crashed shortly after take off from Wonderboom airport. South African Civil Aviation Authority said it will issue a statement with further details on Wednesday.