0418 GMT September 26, 2017
About 475 people were taken to local hospitals in the city of Dezful, some 500 miles (805 kilometers) southwest of the capital, Tehran. Nearly 40 people were hospitalized and the rest were discharged, IRNA reported.
The gas leaked from reservoirs in an abandoned warehouse belonging to the local water supply company.
Dezful, with a population 250,000, is located in Khuzestan Province.