On Monday 28th October Peter and Miranda Harris, co-founders of A Rocha, and Chris Naylor, A Rocha International CEO, together with his wife Susanna, were travelling in South Africa.
In a statement, the charity said: "Miranda, Chris and Susanna did not survive. Peter and the driver of the car are being treated at a local hospital and are in a stable condition. We await further news on their progress.
"Above all, their families and friends are held in our prayers.
"We know that this comes as a profound shock to everyone in the A Rocha Family and others all around the world. A more detailed announcement will be made in due course."
Local reports suggest the vehicle they were travelling in plunged off Swartkops Bridge in Port Elizabeth after colliding with a pick-up truck.
Peter and Miranda Harris founded the charity in 1983 to bring a Christian perspective to the environmental crisis.
The organisation now works in 20 countries across the world.
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