In the history of India, which chemical substance leaked, causing many deaths and blindness?

Good evening. If I remember correctly, it should be the leakage accident of methyl isocyanate, the raw material used in the factory making chemical fertilizers and pesticides in India decades ago. Methyl isocyanate is toxic to human body because it contains cyano group, and the process is not complicated. Please refer to the products after esterification of isocyanate with anhydrous methanol or transesterification of fatty acid ester as appropriate. Most of the known polyurethane curing agent isocyanate volatile gases are harmful to people.