"Iranian physicians reported that victims of the chemical attacks on Halabja showed characteristic symptoms of cyanide poisoning," while other reports indicated substantial quantities of mustard gas and other chemical weapons were used. Most of the wounded taken to hospitals in the Iranian capital Tehran were suffering from mustard gas exposure. A United Nations (UN) medical investigation concluded that mustard gas was used in the attack, along with unidentified nerve agents; the UN's investigator was "unable to obtain any definitive information about the use of hydrocyanic gas as an aggressive chemical." It is generally accepted that "a lethal cocktail of mustard gas and the nerve agents Tabun, Sarin and VX" was used, as reported by the "BBC". Prior to the Halabja incident there were at least 21 documented smaller-scale chemical attacks against Iraqi Kurds, none of which prompted any serious response from the international community.