Four people, including three children, were killed in north Delhi’s Ashok Vihar when a three -storeyed house collapsed on Wednesday morning, police said. “It was an old three-storey building. We are trying to ascertain how old it was and also if it was listed as a ‘dangerous buildings’,” the official said. Seven others are injured in the accident that happened at 9 am. The official are also probing whether the building collapsed due to heavy rains that have lashed Delhi and other north India states in the past few days, killing 25 people. Rescue operation by Delhi Fire service and NDRF are on.