A powdery substance, with effects similar to teargas or pepper spray, was let off in Parliament's public gallery while the Economic Freedom Fighters were being thrown out of President Jacob Zuma's State of the Nation Address.
Dignitaries, citizens and politicians were seen coughing and tearing as they exited one section of the public gallery bay of the National Assembly on Thursday.
Cape Town Mayor Patrica de Lille was one of those affected, as well as African Christian Democratic Party chairperson Kenneth Meshoe.
Both indicated to News24 that they were okay, but could not speak.
Former President Thabo Mbeki was sitting approximately 15m from where the powder was dispersed, but his bay was unaffected.
Eyewitnesses described it as "very strong", causing severe coughing, tearing and a burning sensation in the throat and chest.
The powder appeared to have been kept in a white piece of paper.
Its effects were minimised after Parliament security doused it with water.
Police were monitoring the situation, but there were no leads on a suspect, they said.
It appears as if an ordinary member of the public was the culprit.