A chlorine gas leak from a 900-kg cylinder at a Nagpur water treatment plant around 1 am sent nearby residents fleeing and several people to hospital.
Police evacuated residents within a 200-metre radius as the gas spread into nearby residential areas, causing coughing and breathing difficulties.
The leak was plugged around 5.30 am, after which NDRF, firefighters and water-supply officials secured the cylinder in a caustic-soda water tank.