He said: "We suspect that the plane was on its way to the Wonderboom airport. They will provide an update on any injuries".
Russel Meiring, a spokesman for paramedic company ER24, says the injuries in Tuesday's crash range from minor to critical.
Emer-G-Med Chief Operating Officer Jurgen Kotze said the four critically injured patients were still entrapped in the aircraft.
Paramedic Xander Loubser from BestCare Ambulance Service confirmed the crash happened about 1km east of the N4 in Derdepoort and about 8km east of the Wonderboom Airport.
Best Care ambulance services' Xander Loubser said reports indicated that the charter plane was carrying passengers on an worldwide flight.
Mr Meiring said ER24 helicopters were on the scene to airlift any critical patients to hospital.
"They are busy treating one of the pilots ... and he will be airlifted to a Netcare hospital", he said.
Photos from the scene posted on social media showed the plane, emblazoned with the words "Martin's Air Charter", broken near its front and back ends.
South African Civil Aviation Authority spokesman Kabelo Ledwaba said its investigators were at the scene and would issue a statement.
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