US authorities have confirmed at least 15 people died in flash flooding that swept away two vehicles in a town on the Utah-Arizona border and surged through a nearby national park.
The toll increased on Tuesday night with the discovery that three people had been killed in Utah’s Zion national park when they were caught up in floodwaters rushing through its canyons.
Another four were missing. Their vehicle was found at a trailhead on Monday evening in the Keyhole Canyon area and a search was undertaken on Tuesday morning.
Zion national park is less than 32km north of the small city of Hildale, on the Utah-Arizona border, where 12 people were killed by flash floods on Monday.
Sergeant Brock Bentley of the Washington County sheriff's office in Utah said one person remained missing after the flooding in Hildale, while three children survived.
The wall of water washed the vehicles several hundred yards downstream on Monday afternoon. Authorities said the victims were as young as four. It was unclear if they were all from the same family.
The floods came after heavy rains fell in the canyons just north of the sister towns of Hildale, Utah, and Colorado City, Arizona, sending waves of water barreling through the streets. The community is known as the home base for Warren Jeffs' polygamous sect.
Further inspections of Zion National Park are planned although the National Park Service said the search for the missing hikers had been hampered by concern about flooding and other hazards.
"Another tragedy for our state. Reeling right now," Utah Lieutenant Governor Spencer Cox said on Twitter.
In the small city of Hildale, Utah, hundreds of volunteers were helping search for one person still missing, Washington County officials said, after floodwaters swept through streets.
"It was an act from God," Hildale mayor Phillip Barlow told reporters of Monday's tragedy, according to the Deseret News. "This is something we can't control ... It happened too fast."
Emergency crews have been searching the banks of Short Creek amid sporadic showers, while contractors using heavy equipment have worked to clear thousands of tons of mud and debris. The National Guard has been called in to help with the cleanup.
“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.
An advisory for people to boil their water was issued late Tuesday due to damage to the water system.
Utah Governor Gary Herbert said he was "heartbroken" over the loss of life.
Hildale, home to fewer than 3,000 people, is twinned with Colorado City, across the border in Arizona.
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.
"It's the most terrible thing," said Ross Chatwin, a Hildale resident who is not affiliated with the sect, whose members tend to have little contact with outsiders.
“There has been no confrontation,” Mr Chatwin told the KSL-TV channel of efforts by non-members to help. “They are allowing everyone to come in freely.”
Reporting: Reuters / AP