At least 20 people were injured when two passenger trains collided in the South African administrative capital Pretoria early Thursday, local television reported. The driver of one of the trains was trapped inside the wreckage, with rescue workers at the scene trying to free him. He was believed to be in critical condition, reports said. Hundreds of commuters were estimated to be on the trains at the time of the crash, which occurred at the peak of morning rush-hour. According to broadcaster eNCA, a moving train slammed into the back of a stationary train at a station. The cause of the accident was not immediately clear.