Search-and-rescue teams from Utah, Nebraska, Nevada, California and Missouri have headed to Colorado to aide the largest aerial rescue effort since Hurricane Katrina. Some 1,200 people are still unaccounted for due to flooding in Boulder and other mountain towns. "I’m hopeful that the vast majority of these people are safe and sound," said Gov. John Hickenlooper. "But we do not have any illusions that there could well be more casualties."