Bhuj, June 25: Four persons, including three of a family of scrap collectors, were killed and two others were injured when a crude device exploded near Amisar lake in Bhuj city today, police said. A 10-year old boy, his parents and a cyclist who was passing by were killed in the blast that occurred at around 3.30 pm, they said. The condition of a young boy who was injured in the blast and was being treated at the city hospital was serious, police said, adding senior officials have rushed to the spot and investigations into the incident were being carried out. Bureau Report