Acting Cape Town mayor Brett Heron has condemned the attack on an Intercape bus in Strand in which two people died.
Herron appealed to residents to come forward with information.
“At this stage the reason behind this callous act is still unknown,” he said in a statement.
Two men were killed and 34 other people were injured the bus was petrol bombed on Tuesday evening, the city said.
ER24 spokesperson Werner Vermaak said four people sustained serious injuries and the rest were treated for smoke inhalation and burn wounds.
He said residents of the nearby informal settlement initially thought that shacks were on fire and arrived to see a bus was burning.
Safety and security mayoral committee member JP Smith said the motive for the attack, on Onverwacht Street, just off the N2 highway, was not yet clear.
Safety and security executive director Richard Bosman said there was no unrest in the area and it appeared to be a “random attack”.