Eleven killed in leak of unknown gas in northern India

National Disaster Response Force personnel in Ludhiana, Punjab, India (National Disaster Response Force/AP)

Eleven people have died and four others are in hospital after a gas leak in northern India.

The incident occurred at an industrial area in Ludhiana city, Punjab state, but the source of the gas leak is still unclear, police told the Press Trust of India (PTI) news agency.