Philadelphia police were looking for a silver Lexus IS after its driver struck and injured a police officer early yesterday in Center City.

Officer Samuel Rivera was on a bicycle when he saw the car blocking the intersection at Fourth and South Streets. Rivera asked the driver to move. The driver gunned the engine, moving "in a defiant" manner, said Lt. Frank Vanore, police spokesman.

Rivera and another officer followed the car and ordered the driver to pull over near Third and Lombard Streets. As they approached, the car accelerated again and struck Rivera's bicycle, throwing him from it, Vanore said. Rivera was treated for back injuries at Thomas Jefferson University Hospital and released.

The Lexus, driven by a male, had a partial license plate of HBZ and may have damage on its driver's door, Vanore said. Police asked anyone with information to call 215-686-3013 or 3014. If they see the car, they can call 911, Vanore said. - Jonathan Tamari