At least four people have died in Colorado, where days of relentless rain has caused the US state’s worst floods for centuries.
The National Guard is helping emergency crews carry out mass evacuations across the northeast of the state.
Lieutenant Colonel Mitch Utterback of the Colorado National Guard told reporters: “People are signalling helicopters with lighters and pen lights and little flash lights and little pinch lights on the end of your key chain. Night vision goggles can see that, and that’s how some people are getting picked up.”
Around 500 people are missing and authorities have warned that the death toll is likely to rise.
In Weld County, commissioner Sean Conway said the region was dealing with a “500-1,000 year flood”.