Eleven people have died after a gas leak in northern India.

The leak happened in an industrial area in the city of Ludhiana, Punjab state.

Rajinder Pal Kaur Chhina, a member of the legislative assembly in Ludhiana, said at least nine people had also been taken to hospital.

A team from the National Disaster Response Force has been sent to the site along with a team of experts to determine the cause and source of the leak, she added.

The densely populated area has been sealed off and residents have been evacuated.

“The incident happened near a milk shop and a doctor’s clinic although we cannot say for sure where the leak began,” Ms Chhina told Reuters.

“People who came to buy milk in the morning fell unconscious outside.”

Three of the bodies had “turned blue”, local resident Anjan Kumar said in an ANI news agency video on Twitter.

Ludhiana Deputy Commissioner, Surabhi Malik, told the Press Trust of India news agency it was possible the gas may have spread from manholes.

“We are going to collect samples from manholes. It is quite likely that some chemical reacted with methane in manholes,” she said.

The state’s chief minister, Bhagwant Mann, said the leak came from a factory, tweeting: “All possible help is being provided.”