(CNN) -- Emergency crews in Colorado braved racing floodwaters early Thursday, rescuing a man from a partially submerged car, live on television.
The scene in Lafayette, Colorado, unfolded in video from CNN affiliate KCNC after a night of torrential rain that left at least three people dead. Rock slides and flash flooding collapsed homes, put dams at risk and forced hundreds of people to evacuate.
In Larimer County, a dam break trapped three people, and weather was preventing rescue helicopters from launching to help them.
In nearby Boulder County, emergency officials were getting calls for help "by the dozen" Thursday morning, Boulder County spokesman Andrew Barth said. Crews couldn't reach some places because of debris, mud and steep terrain, he said.
Hundreds of people left their homes. At least one shelter was nearly full, according to the Boulder County Office of Emergency Management.
At least two people died in Boulder County, Sheriff Joe Pelle said. Another person was reported dead in Colorado Springs, in El Paso, County.
One of those who died was trapped in a collapsed building in Jamestown, Boulder County spokeswoman Gabbie Boerkircher said.
The circumstances of the other deaths weren't clear early Thursday, but the Colorado Springs Fire Department said on Twitter that the body had been recovered by a "heavy rescue team."
Rescue workers have not been able to reach isolated canyons and other locations, and Pelle said the death toll could rise.
"This was a devastating overnight storm in the area, and I anticipate that as the day goes on, we are likely to find other people who are victims of this storm," he said Thursday.
Among those in danger: a fire crew whose truck was washed away by water. They were huddled early Thursday on a mountainside, Pelle said.
In the Lafayette rescue, firefighters approached the submerged car on a yellow dinghy, broke out a window and handed the man a life jacket. As he was getting ready to get out of the car, the floodwaters flipped it onto its roof. But a firefighter was able to open the car's door and free the man after a few agonizing seconds.
"I think everybody's heart sank for a minute there," Lafayette Fire Department Battalion Chief Dan Garrett said. "Luckily, everything turned out OK."
The man, whose identity wasn't immediately known, waded out of the water with the aid of firefighters. He was taken away on a stretcher.
The heavy rain overnight turned what is normally a dry drainage ditch into a raging river, according to Sara Farris, a spokeswoman for North Metro Fire Rescue. The force of the water eroded dirt beneath the road, causing a wide section to collapse.
Video from KCNC also showed two other vehicles, one dangling from the edge of a washed-out road and the other in the water under what appeared to be a telephone pole. The man and two others rescued earlier were taken to the hospital for evaluation of minor injuries, Garrett said.
How the incident unfolded -- whether the cars were on the road when it gave way or slid into the gap -- wasn't immediately clear.
Building collapses, dam breaks
Numerous other buildings had collapsed, but it was unclear how many or whether there were any other injuries, Boerkircher said. A rock slide was hampering access to the site.
The Larimer County dam break released a small amount of water and caused flooding to some homes. Three people were trapped, said Sheriff's Office spokesman John Schultz.
Officials called on Colorado National Guard helicopters to help rescue three trapped residents, but the aircraft were unable to launch Thursday morning due to weather, Schultz said.
About 20 miles north of Boulder, in Lyons, water was flowing over the tops of five dams, Boerkircher said. The dams had not broken, but emergency officials were monitoring them very closely, she said.
Officials urged residents in the county of 305,000 people to stay home and off flooded and sometimes impassable roads. City and county offices, schools and the University of Colorado Boulder -- where minor flooding was reported -- were closed Thursday.
The school had to move more than 400 graduate students and research faculty members from family housing units because of flooding, a spokesman said. The school also had to relocate 13 undergraduates from two residence halls, the spokesman said. No injuries were reported on campus.
The chaos is the result of the enormous rainfall overnight: about 7 inches in Boulder, CNN meteorologists said.
"The rain, it almost feels like hail, the drops are so thick," University of Colorado Boulder student Ryan Colla told CNN affiliate KUSA. "It just keeps coming and coming, and when you think it's going to subside, it starts to rain down harder."
The sudden influx of water turned Boulder Creek -- which runs through the city and the university campus -- into a high, fast, muddy and dangerous torrent, Colla told the station.
"It freaked us out," he said.
CNN's Sara Weisfeldt, Tina Burnside, Shawn Nottingham and Sherri Pugh contributed to this report.
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