Washington: The toll in floods that ravaged Colorado in the US climbed to seven, as the biggest rescue operation in the country since the 2005 Hurricane Katrina was mounted.

The Colorado Office of Emergency Management (COEM) confirmed Monday four people drowned in Boulder county, two in Larimer county and one in El Paso county, and that nearly 19,000 homes have been damaged or destroyed by the flooding, reports Xinhua.

Five days of relentless rain caused a run-off from the mountains into the foothills and plains of Colorado’s eastern half.

Thirty highway bridges were destroyed and 40 more were damaged, according to the Colorado Department of Transportation.

Several dams and dozens of roads were washed away.

In Larimer county, bordering the state of Wyoming to the north, about 1,000 stranded residents were airlifted, according to COEM spokesman John Schulz.

Almost 1,300 residents remain “unaccounted for” across the state though that number is dropping as more are being brought to safety.

“It’s massive. We have hundreds of miles of road that are damaged or gone,” Schulz said. “We anticipate a lengthy recovery.”

“Many people here are calling it epic… We’ve had fires and floods, but nothing this widespread…,” Schulz said.