At least six passengers have been injured after an explosion took place in a compartment of Bhopal-Ujjain passenger train in Madhya Pradesh's Shajapur district on Tuesday morning. Bhopal division of Indian Railways Public Relations Officer (PRO) IA Siddiqui said that the reason of the blast is yet to be ascertained. As per a victim the blast occurred because lights inside the compartment blasted. The injured passengers have been admitted to Kalapipal Govt. hospital and the Railways have issued helpline numbers for the assistance to victims and their families.