The passenger bus, bound for Phunsiling in neighboring Bhutan from Assam, had stopped at Chowpati along the Assam-Bengal border, and as the passengers were about to come down, the bomb, concealed in the rear end, exploded.
Official sources said the police had reached the spot and it is yet to be ascertained who was involved in the planting of the bomb.
The injured have been rushed to the Alipurduar civil hospital for treatment.