(NBC News) -- Torrential rain drenched parts of Colorado, washing away homes, swamping roads, and causing at least three deaths as officials worked Thursday to evacuate towns and keep people out of the path of the rising water.
The National Weather Service described a "life-threatening situation" in an emergency message issued just after midnight local time for several areas around Boulder, where about 6.5 inches of rain fell in a 24-hour period, according to the National Weather Service.
The first death was reported near Jamestown, according to officials, and was thought to be because of a building collapse. Another person was found dead on Linden Drive in Boulder, officials said. The Colorado Springs Fire Department reported a third death on Thursday morning after a body was recovered near Interstate 25.
Authorities found the second body while out patrolling in the I-25 area around 5:30 a.m. local time, Colorado Springs Fire Department spokeswoman Sunny Smaldino told NBC News affiliate KUSA.
"We know that we've lost lives and we anticipate that as the day goes on that we may find that we've lost others," Boulder County Sheriff Joe Pelle said at a news conference late Thursday morning.
"This is not your ordinary day, this is not your ordinary disaster," he said. "All the preparation in the world … can't put people up those canyons while those walls of water and debris are coming down."
The sheriff described the status throughout the county as a "continuing, very dangerous situation," shortly before authorities announced they were evacuating residents in the Big Thompson Canyon area and Gov. John Hickenlooper said he had approved a disaster declaration.
The deadliest flood in Colorado history occurred in Larimer County in July of 1976, when the Big Thompson River swelled its banks, killing 144 people and causing more than $85 million in damages, according to data compiled by the University Corporation for Atmospheric Research.
Water reached as high as first-floor windows in some parts of Boulder, a police and fire spokeswoman said. Dive teams were dispatched after cars were seen floating.
"There was one woman that was on top of a vehicle and the vehicle was actually on its side," the spokeswoman said. The rain has also caused mudslides 2 to 3 feet deep in some areas, which are impassable "even if you have an SUV," she added.
Libraries, recreation centers and other Boulder facilities were closed, according to the city's office of emergency management. Energy companies workers were trying to restore power after several flood-related outages, but expected more problems to be reported as the sun rose, according to the emergency office's website.
More than 700 customers were without power on Thursday morning in and around the city of Boulder, according to an outage map maintained by utility supplier Xcel Energy.
Officials said that they evacuated Fourmile Canyon, to the west of Boulder, and Jamestown, to the north. They asked people to remain indoors and off the roads even as flood waters were expected to recede throughout the day.
"It may look OK in your neighborhood, but by the time you get on the thoroughfare to work, you may run into some real issues," Pelle told local newspaper the Daily Camera. "We've got cars in water and debris and manholes missing their covers literally everywhere in the county."
Police in Aurora, just outside Denver, closed flooded streets and reported traffic signal outages. Among those trapped by the widespread flooding were a woman and children in their vehicle, according to local paper the Aurora Sentinel, and police told the paper they were responding to the incident.
The University of Colorado Boulder said on its Twitter account that its campus would be closed Thursday, until officials could assess the storm damage, and some residences were evacuated. Between 400 and 500 graduate students, faculty, and staff are thought to be displaced from on-campus housing units, said university spokesman Bronson Hilliard, and there may be "minor damage" to some buildings. The school will remain closed through Friday.
"We are pleading with students and people on this campus to stay indoors," Ryan Huff, a spokesman for the campus police, said at a press conference early Thursday morning. "It is dangerous out there."
An earth dam in the Big Elk Meadows area collapsed, according to the Larimer County Sheriff's office, causing officials to warn people in the path of the water to be ready to make their way to higher ground if necessary. The sheriff's office said on its Twitter feed that "extrication operations" were underway and that the amount of water thought to have escaped the dam was "relatively small."
The area is thinly populated, NBC News affiliate KUSA reported.
The sheriff's office requested a National Guard helicopter to rescue several families trapped after a road was washed away in Larimer County.
"The road is completely gone," a spokeswoman said. "They have no way of getting out."
Sheriffs in Boulder County were unable to reach the area of the fatality near Jamestown because of thick mud and rock slides.
Authorities have warned people to stay awake from creeks and other waterways as every available fire and police official was out on the streets, Boulder city spokeswoman Sarah Huntley said on Thursday. Flood sirens have been activated along Boulder Creek, and if there are sudden flash floods, "the warnings are going to be short," she said.
Shelters have been opened for evacuated or displaced residents at the YMCA in Boulder, an elementary schools in Jamestown and Lyons, as well as in Longmont and at the Nederland Community Center, according to Boulder's emergency management office. There were about 40 people at the evacuation center in Boulder on Thursday morning, according to Andra Coberly, a spokesperson for the YMCA.