The teargas used by interior ministry troops in Cairo's Tahrir Square is supplied by a US company. Demonstrators say cartridges retrieved from the scene are branded with the name and address of Combined Systems Inc (CSI)...Protesters say the CS gas seems more powerful than that used by Egyptian police during the country's last popular uprising in February. "It's stronger, it burns your face, it makes you feel like your whole body is seizing up," one witness said. [the Resource Centre invited Combined Systems to respond but it has not done so]