DUBAI // Witnesses and a Dubai rescue official say a faulty lift was to blame for the shutdown of the observation deck on the world's tallest tower. The closure has blocked public access to the only part of the Burj Khalifa that has so far opened. Visitors to the viewing floor said there was a loud bang followed by a cloud of dust coming from one of the tower's lift shafts on Saturday evening. Some time later, they say, rescue crews arrived and helped people out of an lift car that had been stuck between floors. Abu Naseer, a spokesman for Dubai's civil defence department, confirmed the incident today. He says 15 people were rescued unharmed.