Paramedics helped survivors out of the aircraft and treated patients at the scene as firefighters tackled the smoking wreckage.
South African Civil Aviation Authority spokesman Kabelo Ledwaba said its investigators were at the scene and would issue a statement.
One person was killed and about 20 were injured when a vintage plane crashed Tuesday after it took off on a test flight from a small airport in the South African capital Pretoria, emergency services said.
The Convair-340 plane built in 1954 was due to soon be flown to the Aviodrome air museum in the Netherlands from Wonderboom airport in Pretoria.
The plane came down on rough ground about five kilometres east of the airport, hitting a small factory building, injuring two people inside.
Images from the site showed the plane broken into several pieces. Paramedics helped survivors out of the aircraft and treated patients at the scene as firefighters tackled the smoking wreckage.
"The plane had 19 passengers on board which includes the pilot and the engineer," Johan Pieterse, the local government emergency services spokesman, said.
"There was one fatality in the cockpit, we are not sure if it's the pilot or the engineer. We have got about 20 patients with injuries ranging from serious to critical, including two people who were on the ground."
Pieterse said the plane hit a small factory premises where two patients were seriously hurt.
The ER24 medical service confirmed the fatality.
The Aviodrome aerospace theme park near the central Dutch city of Lelystad said on its Facebook page that it was "hugely shocked" by the crash.