Police officers found a total of 16 bodies on Tuesday that were swept away with the heavy rainfall that flooded the streets of the state of Utah, one person is believed to be still missing.
Twelve from the 16 people were killed on Monday when a "large wall of water and debris" generated by heavy rainfall, near Utah's border with Arizona, swept them away while they were still in their cars, officials said on Tuesday.
Three of whom were children were saved, but one is still missing.
"In the flash flooding two occupied vehicles were hit by a large wall of water and debris at the Canyon Street Maxwell Crossing and were carried into the Flood," Washington County officials said in a statement overnight.
Search teams were able to find four more bodies - believed to be hikers - on Tuesday in Zion National Park, less than 32 kilometres north of Hildale, three are still missing, officials said.
The administration of the park released a statement saying that the vehicle of the eight hikers was found at a trailhead on Monday evening, after which a search began on Tuesday.
"Another tragedy for our state. Reeling right now," Utah Lieutenant Governor Spencer Cox said in a statement he posted on Twitter.
Hundreds of volunteers were helping out in the search for the one person who is still missing in the small city of Hildale, Utah, Washington County officials said.
"It was an act from God," Hildale Mayor Phillip Barlow told reporters of the Deseret News. "This is something we can't control. It happened too fast.”
Utah Governor Gary Herbert said he was "heartbroken," and that the state has offered its full resources to Hildale to aid the search and rescue effort.
The helping crews have worked since Monday evening keeping an eye on flood crossings and searching the banks of Short Creek under heavy rain showers.
The National Guard has been called in to aid with the cleanup along with the contractors who are operating heavy equipment to clear thousands of tons of mud and debris.
Hildale town of population 3,000 is home to the polygamous Fundamentalist Church of Jesus Christ of Latter-day Saints (FLDS), and whose members tend to have very little contact with people outside their sect.
A flash flood warning was released prior to the rainfall by the National Weather Service alerting all residents to be aware of the weather conditions, but there were many concerns that the message may not have reached members of the FLDS.