ER24 spokesman Russel Meiring said that ER24 paramedics‚ along with several other services‚ were on the scene treating and triaging the injured.
Emergency services were called out to the scene just after 16:00 when the plane was found on fire in a field.
The aircraft, a Convair 340 (ZS-BRV) was taking off from Wonderboom airport. Reports say that there have been no deaths but there are 20 people injured.
Paramedic Xander Loubser from BestCare Ambulance Service said: "There are critical patients".
The plane was likely on its way to Wonderboom airport in north Pretoria, the Tshwane Metro Police Department said.
The plane had been due to fly later this week to Aviodrome via east Africa, through Egypt, Croatia, Austria to the Netherlands.
The Aviodrome aerospace theme park in the Netherlands said on its Facebook page that it was "hugely shocked" by the crash. "Martin's Air Charter" is written on the side of the fuselage.
Civil Aviation Authority investigators were at the scene and started the process of determining the cause of the accident.