Johannesburg gas explosion rips open roads, flips cars during rush hour - 9 injured, buildings at risk

Suspected gas explosion occurred in downtown Johannesburg, South Africa during morning rush hour.
Over 20 vehicles flipped over, roads ripped open, and at least 9 people injured.
Area covering 5 city blocks damaged, buildings at risk of collapse, prompting evacuations.
Gas leak suspected as cause but exact source remains unknown.
No reported deaths so far; search and rescue operations continue.