Severe flooding in the western US state of Colorado has killed at least three people and prompted hundreds of evacuations, officials said Thursday.

Firefighters in the city of Colorado Springs recovered two bodies due to the flooding, they reported on their twitter feed.

A third death was reported in Jamestown, a small town of a couple hundred people, just north of the city of Boulder, Gabrielle Boerkircher, a spokeswoman for the county's emergency management division said.

Rescue workers were just arriving in the town, after mudslides and rockslides had blocked many of the roads with debris, she said.

She was unable to confirm media reports of a fourth death in Nederland, another town nearby.

"It's been raining for the last three days now," Boerkircher said, but the worst "started early in the morning on September 11 and hasn't stopped yet."

A mandatory evacuation order was in place for Jamestown, Boerkircher said, adding that hundreds of people elsewhere in the county had voluntarily gone to shelters, including some 200 people in Lyons and around 400 people at Boulder's University of Colorado campus.

Officials at the university said water had leaked into all the buildings, and their main concern was the library, where damage to the books could be extensive, Boerkircher said.

The flooding is unusual, Boerkircher said, due not just to how much rain has fallen but where.

"It's been a weird storm," she said, adding it had been "turning back around on itself all night. Usually we don't get this amount of rain."

Much of the rain has fallen over a "burn scar" from a forest fire four years ago, she said, explaining that the area "leads into a lot of our creeks and all the creeks end up in our cities."

Boulder County Sheriff Joe Pelle urged residents to "please stay off the roads today," in a message to Facebook, adding "Please leave the roads open for emergency crews."

Schools were closed in the county as were many roads, due both to flooding and downed trees or debris.

And officials were warning residents especially to steer clear of Lefthand Canyon where there were reports of a 15 foot wall of water that prompted one fireman to take refuge in a tree -- where he was still awaiting rescue, Boerkircher said.