The leak occurred on Sunday morning in the city of Ludhiana, leaving 11 people dead and four in hospital. The area was sealed off and residents were evacuated after many people reported breathing difficulties. The cause of the leak has not been officially confirmed yet but reports say that high levels of hydrogen sulphide gas were detected in the area. A district official had said on Sunday that a chemical may have reacted with methane in manholes to produce the deadly vapour. A team from the National Disaster Response Fund is investigating the source of the gas leakage. "My cousin's entire family was killed," says Kapil Kumar, who lived in the neighbourhood where the leak took place. "There were five people living in the house. Now there is no one left."