The N4 is closed near Machadodorp following an accident involving a truck carrying explosives.
TRAC advised road users of the closure about two hours ago.
“As a result (of the accident), a total road closure is required to make the scene safe.
“The relevant authorities are dealing with the matter according to the required safety protocols.”
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The time before reopening the N4 is yet to be determined and TRAC advised that traffic using the N4 between Mbombela and Belfast use alternative routes, either via Lydenburg or Barberton.
“We urge motorists to be cautious of road conditions on alternative routes.”
TRAC said it would provide updates regarding the situation as more clarity on the estimated time to clear the scene becomes available.