BOGOTA, Colombia -- More than 1,000 people may have died in the earthquake and mudslides which devastated a Colombian river valley last Monday, an official at the government's National Disaster Prevention Office said Thursday."From what we are seeing and given the difficulty of finding a lot of people, we can't rule out the possibility that the number of victims is higher than 1,000," Juan Manuel Uribe, an assistant to the office's director, said.The government had previously said at least 250 people died in the disaster but local residents consistently claimed that the total was much higher.As rescuers aboard a fleet of helicopters continued their search for survivors in the mainly Indian Paez valley 300 kilometers southwest of Bogota in howling winds and rain, officials said the tragedy was much worse than they first thought."The damage is really terrible," Defense Minister Rafael Pardo Rueda told reporters after a brief visit by air to the disaster zone. "The images of the disaster are horrible."