Fifteen people, including six children, have died in flash flooding that struck the US state of Utah overnight.
Twelve of the victims were from two families in their cars, who were caught off guard by the raging waters in the small town of Hildale, officials say.
"At about 5:00pm, two vehicles were hit by floodwaters and were swept into the flood," local official Michelle Catwin said.
"This is the biggest flood we have ever seen."
She said three other people travelling in the two cars survived, and one was still missing.
Witnesses said the drivers of the two vehicles tried to back away from the floodwaters barrelling through the streets, but were swept away.
Further north, three people were killed by flash flooding in Zion National Park and four remain missing.
"Rangers received a report of a group of seven individuals canyoneering in Keyhole Canyon shortly before the flooding began (on Monday afternoon)," emergency officials said in a statement, adding that rescue efforts were being hampered by continued rain.
A flash flood warning was still in effect at the park on Tuesday, with rivers and streams swelling to dangerous levels.
Hildale is located around 500 kilometres south of Salt Lake City.