<human>:  When did the Bhopal gas tragedy happen?
<bot>: The Bhopal gas tragedy happened on the night of December 3, 1984. It is the world's worst industrial disaster, in which at least 4,500 people died, and many more were injured. It occurred in the city of Bhopal in the state of Madhya Pradesh, India. The Union Carbide plant was releasing methyl isocyanate gas into the air. It is estimated that the gas cloud killed over 2,000 people immediately, and as many as 25,000 more people died in the months and years following the disaster.