Doctors report seizures and convulsions as witnesses claim that different crowd control versions are being used.

Egyptian security forces are believed to have used a powerful incapacitating gas against civilian protesters in Tahrir Square following multiple cases of unconsciousness and epileptic-like convulsions among those exposed.

The Guardianhas 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, also known as Mace, which was the crowd control gas used by the U.S. before CS was brought into use; and CR gas.

Some protesters report having seen canisters marked with the letters “CR” although theGuardianhas not been able to confirm this independently. Both gases can be more dangerous than CS and can cause unconsciousness and seizures in certain circumstances.

Concern began to emerge over the use of more powerful incapacitating agents after reports of gassed protesters falling unconscious and having attacks of jerking spasms.

Those who have experienced the more powerful gas have described it as smelling different and causing an unusual burning sensation on the skin. Others have complained of rashes.

In one field clinic, set up in a mosque near Tahrir Square, aGuardianvideographer recorded footage of a young man brought in insensible and convulsing, whose symptoms have been typical of those seen in recent days in Cairo.

A doctor treating him described both the symptoms and the gases used. “We have been attacked with four different kinds of gas bombs,” said Dr. Ahmad Sa'ad. “I have never seen these ones before because the patients come in with convulsions. I've never seen patients like that before. You can see it yourself. You can be 100 metres away from the gas bombs [and it will still affect you].” Similar reactions were reported earlier this year in Yemen where demonstrators also suffered convulsions after being hit with old stocks of CN gas held by the regime.

Another concern, raised by the group Campaign Against Arms Trade, is over the age of some of the CS gas that has been used by Egyptian security forces. Gas canisters more than five years old can become more toxic, and some canisters that have been used in the last few days are up to a decade old.

Karim Ennarah, who works with the Egyptian Initiative for Personal Rights, has been trying to collect evidence about the gases used in Tahrir and the surrounding area since the weekend, and in what circumstances, amid claims the gases have been used in a way that violates international norms.

“The basic principle of the way the gas is being used is not for riot control but as a punishment and that raises questions of violations of its use.”

© Guardian Newspapers Limited, 2011

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