Islamabad, Aug 15 (IANS) At least two people were killed and around 20 others injured on Thursday in a collision between a troller and a van in the southern port city of Karachi, the rescue service reported.The accident took place early morning on the Northern Bypass of the city when the troller hit the van from behind as both vehicles were going in the same direction, resulting in the casualties, Xinhua news agency reported.Rescue workers reached the site and shifted the victims to a local hospital, said the rescue service, adding that one of the injured was in critical condition.The authorities said that an investigation is underway.Further details are awaited.