The Guardian reports: Egyptian security forces are believed to be using a powerful incapacitating gas against civilian protesters in Tahrir Square following multiple cases of unconsciousness and epileptic-like convulsions among those exposed.

The Guardian has collected video footage as well as witness accounts from doctors and victims who have offered strong evidence that at least two other crowd control gases have been used on demonstrators in addition to CS gas.

Suspicion has fallen on two other agents: CN gas, which was the crowd control gas used by the US before CS was brought into use; and CR gas.