At least 200 pupils were admitted to hospital after a gas leak near their school in southern New Delhi, Indian police said.

Classes were under way at the government-run girls' school in Tughlakabad when gas leaked from a container parked at a depot close to the school and filled with a chemical meant for industrial use, officials said.

"The children complained of irritation in the eyes and throat and were immediately evacuated and sent to three hospitals nearby," Romil Baaniya, deputy commissioner of police, told reporters.

"No one is serious. The situation is normal now," he said, adding that more than half of those admitted to hospitals have been released.

Police will initiate legal action against the handlers for negligence, Baaniya said.

Deputy fire chief Rajesh Panwar said, however, the source of the gas leak remains unclear.

Officials said they have ordered an investigation into the source of the gas leak [Rajat Gupta/EPA] 

A teacher at the school told NDTV news channel that when the pupils complained of discomfort, they were gathered in the school grounds.

"The smell of gas became stronger and we shifted them out of school and some to the hospitals," she said.

Manish Sisodia, New Delhi's deputy chief minister who is in charge of education, said he had ordered an investigation.

Gas leaks are not uncommon in India, with most caused by a failure to comply with safety standards.

In 2014, a poisonous gas leak at one of India's largest steel plants in central Chhattisgarh state killed six people.

A toxic gas leak in Bhopal city in 1984 killed at least 25,000 people and remains the world's worst industrial disaster.

Source: News agencies