Around 200 schoolgirls were committed to hospital in Delhi after a gas leak.
Police have said that the leak came from a container depot close to the girls’ school in the Tughlakabad area.
The pupils complained of irritation to their eyes and throats, leading to the school being evacuated. They are not thought to be at serious risk.
The gas is believed to be chloromethyl pyridine, a chemical which is used in the manufacture of pesticides and insecticides.
India's National Disaster Response Force is working with police to determine how the chemical leaked.