Update as of 2:46 a.m. EDT: Four hikers from a group of seven have been killed in Zion National Park in Utah, bringing the death toll from flash floods in the state to 16, according to media reports. A total of four people in the park and the border town of Hildale remain missing. 

Original story:

The death toll from flash floods that hit the western state of Utah rose to 15 Tuesday with five people still missing in the small town of Hildale and nearby Zion National Park. Rescuers found bodies of several children late Tuesday in the polygamous town on the Utah-Arizona border.

Flash floods washed two vehicles off the road at Canyon Street and Williams Avenue in Hildale, which is located about 45 miles south of the park. A total of 16 people were in the two vehicles, local media KUTV reported. Three people survived the incident and one remained missing, bringing the death toll in Hildale town to 12 Tuesday. Six of the victims were children, according to Agence France-Presse (AFP).

"At about 5:00 pm, two vehicles were hit by floodwaters and were swept into the flood," Michelle Catwin, a local official, told AFP. "This is the biggest flood we have ever seen."

Utah flash flood_4 People look at the damage caused by a flash flood in Hildale, Utah, on Sept. 15, 2015. Photo: Reuters/David Becker

Three people were killed by flash flooding in Zion National Park and four remain missing, authorities said Tuesday.

"Rangers received a report of a group of seven individuals canyoneering in Keyhole Canyon shortly before the flooding began (Monday afternoon)," emergency officials said, in a statement, adding that continuous rain hampered rescue efforts while a flash flood warning remains in place at the park.

Utah flash flood_1 Residents search along the Short Creek after a flash flood in Hildale, Utah, on Sept. 15, 2015. Photo: Reuters/David Becker

Workers from agencies in four counties in Arizona and Utah -- Washington, Mojave, Kane and Coconino -- joined the search Tuesday and National Guard troops were expected to arrive Tuesday night.

Utah Gov. Gary Herbert said Tuesday he mourned the lives lost in Zion and the border towns.

"Today's tragedy also serves as a reminder to residents and those visiting our state to take appropriate precautions and be aware of the factors that contribute to dangerous flash floods," Herbert said in a statement, according to the Associated Press.

Utah flash flood_3 Rescuers walk along the bank of Short Creek while searching for missing residents after a flash flood in Hildale, Utah, on Sept. 15, 2015. Photo: Reuters/David Becker

“A roaring river, just a wall of mud and debris, ripping up trees,” Pamela Black, 63, a resident of Hildale, told the New York Times. “We knew it would flood, because it always does when there’s a downpour, but never anything like this.”

Authorities also issued an advisory for Hildale and Colorado City residents urging them to boil water before drinking as it could be contaminated as a result of the flooding.

“Mainline sections have been affected by the flooding, and we are taking samples to confirm the status of the water quality,” Utah Emergency Management said.