At least 13 people were killed and over 20 injured when a bus and a pick-up truck carrying gas cylinders collided head-on in Bangladesh's Faridpur district, a police official said on Saturday.The accident took place on a highway connecting Dhaka and Khulna town on Friday night.The official told Xinhua news agency that the collision sparked a huge fire and the toll might increase since some of the injured were in critical condition."Fire fighters recovered 13 charred bodies from inside the bus," he said.The cause of the accident is being probed.