Colorado flooding death toll rises as thousands warned to evacuate

The death toll from severe flooding in the US state of Colorado has risen to four, as authorities warn thousands to evacuate Boulder and outlying areas.

The body of an unidentified Boulder woman was found after she was swept away from her submerged vehicle on Thursday, authorities have said.

All Boulder County offices were closed on Friday as rainfall was expected to continue overnight.

As many as 80 people remain unaccounted for, officials say.

Days of heavy rain have caused severe damage to property and forced the rescue of more than 2,500 people, Boulder County authorities have said.

More than 15in (38cm) of rain - nearly half the region's annual average - has fallen in a single week, according to the National Weather Service.

President Barack Obama has signed an emergency order approving federal disaster aid for Boulder County.

Towns such as Jamestown, Lyons and Longmont are said to have been reduced to islands by the swirling floodwaters.

'Biblical'

Officials set up road blocks to prevent some residents fleeing in their vehicles over submerged or debris-strewn roads.

The raging torrent - dubbed a "100-year flood" by officials - has prevented rescue crews from reaching communities stranded downstream.

Lyons resident Howard Wachtel joked to the Associated Press news agency: "This is more like something out of the Bible. I saw one of my neighbours building an ark."

Some 4,000 people living along Boulder Creek were sent notices warning them to move to higher ground late on Thursday, reported Boulder's Daily Camera newspaper.

Another 500 inhabitants of Eldorado Springs were urged to leave due to a threat from South Boulder Creek, an official told the Associated Press early on Friday.

Low-lying areas beyond the Rocky Mountains were also at risk, with up to 3,000 people already ordered to leave the Commerce City district of Denver.

Police in the city reported on Twitter a man was pulled by the water into a drainage pipe with his dog. Both were rescued alive two blocks away.

'Mud, muck, debris'

Governor John Hickenlooper told local radio there had been "a staggering amount" of rainfall.

Floodwaters erupt out of a sewer on Canon Avenue in Manitou Springs, Colorado.

A home was left cut off in Golden, Colorado, after a bridge was destroyed

The St Vrain river was among several waterways that topped their banks early on Thursday morning

High water rushes through Boulder Creek in downtown Boulder

A man sorts through debris that washed down to his home

"Given the drought situation we've had, it was almost a year's worth of rain," he said on the KBCO radio station.

"There is water everywhere," Andrew Barth, emergency management spokesman in Boulder County, told Reuters news agency. "We've had several structural collapses. There's mud and muck and debris everywhere. Cars are stranded all over the place."

National Guard troops have reportedly been dispatched north of Boulder to the cut-off town of Lyons, which is said to be without fresh water, power or phone lines.

Lyons resident Jason Stillman and his fiancee were forced to flee their home when a nearby river began to overflow into the street.

"There's no way out of town. There's no way into town. So, basically, now we're just on an island," he told USA Today.

Part of US highway 36 was closed after it was washed out, and Colorado officials shut Interstate 25 north of Denver all the way to the Wyoming border.

A 20ft (6m) wall of water was reported in Left Hand Canyon, north of Boulder, according to National Weather Service meteorologist Bob Kleyla.

The prolonged rain has been blamed on a low-pressure weather system hovering over Nevada which is drawing moist air out of Mexico into the Rockies' foothills.