A BMW 4 Series, which was travelling along Eastern Avenue towards Nelson, collided with a tree at around 10.40am on Saturday (July 2).
The driver, a man in his 20s, and a 16-year-old boy, who was a passenger in the car, suffered “serious leg injuries”.
They were taken to Royal Preston Hospital for treatment.
“We would like to hear from anyone who saw the collision or saw the vehicle in the moments before,” a spokesman for Lancashire Police said.
“If you saw anything or you have footage on dashcam or CCTV, please get in touch.”
Anyone with information should contact police by calling 101, quoting log number 1522 of July 2.