National Guard helicopters and truck convoys carried the admonition into paralysed canyon communities where thousands of stranded residents were eager to escape the Rocky Mountain foothills. But not everybody was willing to go. Dozens of people in the isolated community of Jamestown wanted to stay to watch over their homes.

Authorities made clear that residents who chose not to leave might not get another chance for a while. Rescuers won’t go back for people who insist on staying, Boulder County Sheriff Joe Pelle said.

"We’re not trying to force anyone from their home. We’re not trying to be forceful, but we’re trying to be very factual and definitive about the consequences of their decision, and we hope that they will come down," Mr Pelle said.

Special education teacher Brian Shultz, 38, was torn about leaving his Jamestown home. "I was thinking about staying. I could have lasted at least a year. I have a lot of training in wilderness survival," he said, adding that he probably had enough beer to last the whole time.

As he sat outside a makeshift shelter at a high school, Mr Shultz floated the idea of walking back into the funky mountain town. "If we hike back, I would stay there and just live. I’d rather be at our own house than staying at some other people’s houses," he said. His wife, Meagan Harrington, gave him a wry smile. About 10 of their neighbors declined to evacuate, she said. "They said they wouldn’t force you, but it was strongly encouraged," she said.

Mr Shultz teared up behind his sunglasses as he compared his situation to that of his neighbours. "At least all of our stuff’s there and will be there when we get back. The people right by the river, their houses were washed away. Other people thought their houses were going to be OK, and then they started to go. It’s just really devastating."

Across the foothills, rescuers made progress against the floodwaters. But they were still unable to go up many narrow canyon roads that were either underwater or washed out.

On Saturday, the surge of water reached the plains east of the mountains, cutting off more communities and diverting some rescue operations. Rain was expected to start up again in the mountains and foothills, with between a half-inch and 2 inches forecast to fall overnight Saturday, according to the National Weather Service.

Four people have been confirmed dead since the  floods began Wednesday. And hundreds of others have not been heard from in the flood zone, which has grown to cover portions of an area nearly the size of Connecticut.

Some of those who are unaccounted for may be stranded or injured. Others might have gotten out but not yet contacted friends and relatives, officials said. Police expected to find more bodies as the full scope of damage emerges.

A woman was missing and presumed dead after witnesses saw floodwaters from the Big Thompson River destroy her home in the Cedar Cove area, Larimer County sheriff’s spokesman John Schulz said.

"I expect that we’re going to continue to receive reports of confirmed missing and confirmed fatalities throughout the next several days," he said.

Two fatalities were identified by the Boulder County coroner Saturday as Wesley Quinlan and Wiyanna Nelson, both 19. Authorities believe the couple died when they were swept away after driving into floodwaters and then leaving their vehicle. Their cause of death is under investigation.

The military put more troops on the ground and helicopters in the air to aid in the search-and-rescue effort. By Saturday night, 1,750 people and 300 pets had been evacuated from Boulder and Larimer County, National Guard Lieutenant James Goff said.

More than 85 fifth-graders from Louisville were greeted by their parents and friends Saturday after they were rescued from an outdoor education centre near Jamestown.

The airlifts were to  continue Sunday with helicopter crews expanding their searches.    It was not clear how many people were still stranded.

A helicopter taking Governor  John Hickenlooper on a tour of the flooded areas even got in the act, stopping twice to pick up six stranded people and their two pets. Terry Kishiyama’s son flagged down a helicopter with his shirt after a three-day wait for rescue from a neighbour’s house on higher ground.

"You could hear the choppers for miles and miles, but I didn’t know if they were evacuating people. You see a chopper going down behind a ridge, and you have no clue," Mr Kishiyama said.

In addition to his son’s efforts, Mr Kishiyama said his wife shouted at the chopper, "We have babies!"

Above Larimer County, rescue crews airlifted 475 people to safety and planned to resume helicopter searches on Sunday, weather permitting. Crews also used inflatable boats to pick up families and pets from farmhouses on Saturday. Some evacuees on horseback had to be escorted to safe ground.

Near Greeley, 35 miles east of the foothills, broad swaths of farmland had become lakes, and the raging South Platte and Poudre rivers surrounded more homes.

In one Boulder neighbourhood, residents turned back city crews and machinery that arrived to remove the makeshift berms and sand-filled trash bags protecting their homes. University of Colorado students helped homeowners improvise a way to divert the rising water from Gregory Creek.

"The residents know better than anybody else how the water flows through the neighborhood," said Colleen Scanlan Lyons.

In communities where floodwaters began receding, homeowners had a chance to assess damage. In Laporte, Wendy Clark surveyed soggy carpets and furniture that got damaged by the Poudre River. "This mud smells disgusting," she said. "I don’t know how long that’s going to be around."

Associated Press