AlHijjah 8, 1432, Nov 4, 2011, SPA -- Police said a tram collided into two others after failing to brake in the Polish city of Wroclaw, injuring 21 people, including four children, according to AP. Wroclaw police spokesman Krzysztof Zaporowski said it was not immediately clear whether mechanical failure or human error caused the crash on Friday. The tram failed to brake and rammed into two other trams, one behind the other, at a stop. Zaporowski said those hurt were taken to hospitals in the southwestern Polish city with injuries mostly to their spines and limbs. Police and prosecutors have opened an investigation.