By air and by land, the rescue of hundreds of people stranded by epic US mountain flooding has accelerated as debris-filled rivers became muddy seas that extended into towns and farms miles from the Rockies.
Helicopters and hundreds of National Guard troops on Saturday searched mountainous terrain for people as food and water supplies ran low in remote communities cut off since Thursday.
Thousands were being driven from their homes in convoys.
For the first time since the harrowing floods began on Wednesday, Colorado got its first broad view of the devastation.
Floodwaters have affected parts of a 11,655-square-kilometre area - an area the size of the US state of Connecticut.
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A woman was missing and presumed dead after witnesses saw floodwaters from the Big Thompson River destroy her home, Larimer County sheriff's spokesman John Schulz said.
"We're sure there are going to be additional homes that have been destroyed, but we won't know that for a while," Schulz said.
"I expect that we're going to continue to receive reports of confirmed missing and confirmed fatalities throughout the next several days."
Four people have been confirmed dead since the harrowing floods began on Wednesday.
More than 170 people remained unaccounted for in Boulder County, but that number could include people who are still stranded or who escaped but have not made contact yet, said Boulder County Sheriff Joe Pelle.
Still more rain was expected on Saturday. And the outlook for anyone who preferred to stay behind was bleak: weeks without power, mobile phone service or running water.
"Essentially, what they were threatening us with is, 'If you stay here, you may be here for a month,"' said 79-year-old Dean Hollenbaugh, who was evacuated by helicopter from Jamestown, north-west of Boulder.
