Nearly two dozen helicopter crews have fanned out across the embattled state of Colorado, where flooding has wreaked widespread devastation. The choppers have been dropping food and supplies in what sources say is the biggest air rescue since Hurricane Katrina.

New video, shot by a drone, shows the horrific scope of the flooding, the devastation of which is something authorities say could take years to recover from.

At least eight people have now been killed in the natural disaster, and the search continues for hundreds of people who remain missing.

A week of torrential downpours in the eastern Rocky Mountains has left a rising death toll and left as many as 658 unable to contact authorities or loved ones.

Rescuers grounded by weekend rains took advantage of the break in the weather on Monday to resume searches for people still stranded, with 21 helicopters fanning out over the mountainsides and the plains to drop supplies and airlift those who need help. Earlier in the day the helicopter crews -- flying out of Boulder -- were grounded.

The Federal Emergency Management Agency sent two 80-person search-and-rescue teams to assist with continuing rescues in Larimer County and provide aid to other communities following massive flooding that began Wednesday. Large military vehicles were attempting to get up the mountain roads.