BAGHDAD - Officals say more than 200 people were sicked by a chlorine gas explosion at a water purificiation plant in southern Iraq.

Dr. Saadoun al-Aalak, deputy director of Al-Sadr hospital in Amarah, says no one died in the Thursday evening blast at a water purification plant there. He says four people who were hospitalized overnight in critical condition from breathing the poisonous gas were released Friday morning.

The provincial governor, Sheyaa al-Sudani, says 200 sickened Iraqis initially sought medical treatment but most recovered quickly.

The cause of the blast in Amarah, about 320 kilometres southeast of Baghdad, was not immediately known, but there was no immediate indication of an attack.