At least six people were injured in a bomb explosion on a bus in the eastern Indian state of West Bengal Sunday, a senior police official said. \"The bomb exploded on the bus in the state\'s Jalpaiguri district when it halted for lunch for passengers. The bus ferries passengers between Thimpu and Phutsholing in Bhutan and the blast happened when it took an unscheduled stop in Jalpaiguri district near the India-Bhutan border,\" the official said, on condition of anonymity. Only 10 to 12 passengers were on the bus when the explosion happened as most were having their lunch at a small eatery, he said. \"All the injured have been admitted to a local hospital where the condition of some are said to be serious,\" the official said. A probe has been ordered into the incident, he added.