Heavy flooding in Boulder County, Colorado
13 September 2013 Last updated at 19:06 BST
Thousands more people have been warned to evacuate the Boulder area of Colorado as floodwaters hit roads and properties.
Storm rains have killed three people in the state and caused severe damage to property.
Water levels in the Boulder Canyon are reportedly rising rapidly because of debris and mud blocking its mouth.
Alastair Leithead reports.