Island plant during a 45-minute period. The venting was due to a relief valve operating to prevent overpressure of a liquid ammonia tank. Engineering studies subsequently revised the amount down to ~. The leak was identified by firefighters responding to an alarm raised by the hospitalisation of two railway workers at who were affected by the plume of escaping gas. Six fire units and a hazardous chemicals unit were called to the chemical plant to deal with the leak of the ammonia gas. Despite initial statements by Orica that the leak posed no public health risk, two rail workers in the nearby suburb of were overcome by ammonia fumes and were taken to hospital with breathing difficulties. Less than an hour before the ammonia leak, the Environment Protection Authority announced it would take Orica to court over the hexavalent chromium leak which occurred on 8 August 2011 at the same plant. Ammonium nitrate leak, 2011 On 7 December 2011, in excess of of weak ammonium nitrate (<35%) solution/fertiliser leaked onto grassed areas at the Kooragang Island chemical plant. Emergency services were called to the site including a HAZMAT team. The spill occurred less than a day after the Environmental Protection Agency announced it would allow the reopening of part of the Kooragang Island plant. Local residents continued to criticise the company for failing to notify residents in a timely manner and called for the plant to remain closed. Hydrogen stack fire, 2012 On 8 January 2012 lightning ignited hydrogen being released from the plant. Flames higher than leapt from the hydrogen stack and were reported by local residents to authorities. Port Kembla, New South Wales Sulphuric acid leak, 2011 A spill of approximately of concentrated sulphuric acid occurred at the chemical plant on 16 December 2011. The leak was suspected to be caused by a hole in the ship-to-shore pipeline. Acting chief environmental regulator Mark Gifford from the NSW EPA said he was concerned about the ongoing incidents with Orica. In Mexico Coahuila Explosion, 2007 On 10 September 2007, 28 people were killed and over 250 injured in Coahuila, Mexico, as a result of an accident between a pick-up and a truck which resulted in an explosion. The truck was transporting about 25 metric tons of dynamite under contract for the company Orica near the cities of Monclova and Cuatro Ciénegas. Exact numbers of the dead and injured vary according