Media playback is unsupported on your device Media caption Thousands of homes have been destroyed by the floodwaters

Emergency teams are searching for hundreds of people still missing after Colorado's deadly floods.

State officials say more than 300 are still unaccounted for, but many are believed to be merely cut off in remote areas inundated by the historic rains.

Several towns were encircled by raging waters. More than 3,000 people have been evacuated by air and ground.

The floods have been blamed for eight deaths, 1,500 homes destroyed and another 17,000 properties damaged.

Days of rain was followed by a flash-flood rainstorm in the early hours of Wednesday last week.

'Astronomical'

Colorado Office of Emergency Management spokeswoman Micki Trost told the BBC on Tuesday night that 306 people were missing: 109 in Boulder County and another 197 in Larimer County.

By Tuesday, military helicopters had flown almost 2,400 people and more than 850 pets to safety, in what National Guard officials say may be the largest airlift since Hurricane Katrina in 2005.

The flood zone covers parts of or all of 17 Colorado counties, in the normally semi-arid region around the state's major cities.

The downpour dumped about 21in (53cm) of rain in parts of Boulder city, nearly double the area's average annual rainfall.

Media playback is unsupported on your device Media caption Aerial shots of Colorado flooding

As calls for emergency rescues taper off, rescue crews with the US National Guard are identifying new areas to check and places to cover again.

But it is expected to take weeks or possibly months to search through all the flooded areas and confirm a final death toll.

Helicopter crews are also dropping food and water to those still stranded, the BBC's Alastair Leithead reports, and the relief operation is now focusing on providing emergency housing.

It could also be months before the water can be drained away from some areas, and much longer for homes to be repaired and rebuilt, says our correspondent.

Officials have also begun using helicopters to survey damage to roads and bridges washed out by floodwaters.

More than 400 lane-miles (643km) of state highway and some 30 bridges are destroyed or impassable.

Media playback is unsupported on your device Media caption Footage shows the rescue of a man who survived in an air pocket after his car was submerged, as Elham Rizi reports

In Weld County, bordering Wyoming, 654 miles of roads are damaged. In Boulder County, damage includes 150 miles of road, along with hundreds of bridges, culverts and canals.

Officials are expecting a long rebuilding period - and an expensive one.

"It's going to be astronomical, there's no way around it," Captain Ralph Kettle of the Poudre Fire Authority in Fort Collins told the Associated Press news agency.

President Barack Obama has signed a disaster declaration in the wake of the flooding, which allows federal emergency aid to be used in the state.

An initial $5m (£3.1m) has been pledged but it is unknown how much total federal funding Colorado will receive to rebuild.