At least eight people were killed near Utah's border with Arizona when flash floods triggered by heavy rain in nearby canyons swept them away in their cars, officials said on Tuesday.
Five people were missing, Washington County officials said, and one person remained in hospital after a "large wall of water" swept through streets around the small city of Hildale, Utah on Monday.
A flash flood warning for the area remained in effect on Tuesday morning. Thunderstorms were forecast in the afternoon.
"Six of the deceased were located in Utah and two in Arizona, almost two-and-a-half miles downstream," the county officials wrote in a Facebook post.
They said crews worked through the night monitoring flood crossings and searching the banks of Short Creek, and contractors using heavy equipment worked to clear thousands of tons of mud and debris.
"Rain continued throughout the night - flooding has continued and all crossings remain closed," the officials said.
Hildale, home to fewer than 3,000 people, is twinned with Colorado City, across the border in Arizona, where officials were due to hold a news conference later on Tuesday.
Both cities are home to the polygamous Fundamentalist Church of Jesus Christ of Latter-Day Saints. That sect is not affiliated with the Salt Lake City-based Church of Jesus Christ of Latter-day Saints, which renounced polygamy in 1890.
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