Swaraj Puri was preparing for bed when he heard a man shouting. It was a pleasant, cool, night, he remembers. Bhopal's chief of police went outside.
"I had young children and I didn't want them to be woken," he says. "I asked what the problem was. He said there was something happening in the Carbide area."
Sitting sipping chai on a leafy veranda overlooking the outskirts of Bhopal, former police chief Puri remembers the events of 1984 as if they were yesterday.
"So I went to see for myself. You could see the cloud of gas moving in front of you. People were coughing. My eyes were watering. I thought: my God, what has happened?"
By daybreak the scale of the disaster became clear. It fell to Mr Puri and his men to begin collecting the bodies.
Watching how events unfolded
Take footage of the disaster into the slums that surround the Union Carbide plant and a small crowd immediately gathers. People strain to spot themselves among the images of coughing children.
One man identifies his mother, but says she died many years ago. He thinks the shot of a boy, coughing helplessly beneath a blanket, may be his brother.
Hasira Bi cries at the memory of that night. She lives today in the same small shack where she was sleeping on the night of the explosion, just a stone's throw from the factory's gates.
She remembers waking around midnight, noticing a noxious smell in the air. Outside, people were running in all directions.
"There were dead bodies everywhere," she recalls, standing on the main road opposite the factory wall. "There was a dairy and all the buffalos were dead. People were in the street wearing what they'd worn to bed, just in their underclothes."
Hasira bundled her family together and joined the crowds fleeing the gas. It was only later that she realised she had left one of her sons at home.
She returned to find him lying unconscious on a handcart, left for dead. She has been wracked with guilt, ever since.
Michael Blakey was also caught up in the events of 1984. He worked for the BBC at the time as a sports reporter. He was in India covering the England cricket team's tour and remembers receiving a phone call about "a small gas leak in a place called Bhopal".
"At first they said not to worry about it," he says. "But then I got another call saying 'get on a plane'.
"You couldn't believe the smell, the misery. It was absolutely awful," he says. "You woke up in the morning, if you got any sleep, and there was just this sound of coughing. Everywhere, people were coughing".