Johannesburg firemen are combating an underground cable fire in the CBD.

Firefighters in Johannesburg's central business district are battling an underground fire along the M1 on Wednesday. 

The fire was reported early Wednesday morning.

A huge part of the road was clouded by thick smoke.

According to Robert Mulaudzi, spokesperson for the Gauteng emergency services, the cause of the fire is still under investigation.

"The majority of energy is supplied to Braamfontein and the neighboring areas via underground lines. We have asked our City Power colleagues to open the tunnel while we continue to suppress the fire.

"The fire has affected a portion of the highway, primarily Smith Street. We are extinguishing the fire to the west, and we urge our drivers to use caution when driving in that area.

So far, the area between Empire and Crown Interchange has been closed off, so we are encouraging cars to avoid it while we continue to extinguish the fire.

"In terms of electricity interruption, City Power will give feedback on which areas might be affected by this underground fire."

According to Mulaudzi, there have been no injuries reported.

By: Radebe Khumbuzile