An Engen petrol tanker overturned in Kempton Park at the Voortrekker Road offramp on the R21 on Monday morning.
While it was unclear what caused the tanker to jackknife, the accident resulted in the spillage of fuel on the freeway, causing major traffic congestion.
The Ekurhuleni Metropolitan Police Department (EMPD) was on the scene redirecting traffic and motorists have been urged to avoid the route.
This is a developing story. More to follow.