-SALT LAKE CITY (AP) -- Two sisters aged 7 and 3 died in flash flooding that sent torrents of water roaring into a narrow canyon in the Utah desert, authorities said Tuesday.
At least 21 others escaped the flooding Monday afternoon in Little Wildhorse Canyon, where the curving sandstone walls are so narrow at points that hikers must turn sideways to walk through.
The girls were hiking with their father and mother when the storm hit. The father found his 7-year-old daughter's body before authorities were called to the scene, according to Emery County Sheriff's Office spokesperson Janalee Luke. Their names were not immediately released.
The family from the Salt Lake City suburb of West Jordan was camping in the area for Mother’s Day, the Deseret News reported.
The 3-year-old sister was found Tuesday, after dozens of searchers combed the area for hours with the help of helicopters about 200 miles (320 kilometers) south of Salt Lake City. A piece of her clothing was found in a wash miles away.
The others who escaped were with different groups, Luke said.
Flooding hit after an isolated thunderstorm storm crossed nearby Goblin Valley State Park, known for its otherworldly bulbous stone formations.
Little Wild Horse Canyon is considered a popular, family friendly trail that displays awe-inspiring colorful stone walls, but flash flooding is a risk in the narrow formations known as a slot canyons.
Desert rains can be dangerous because the hard earth doesn't soak up much water. Instead, the rain collects quickly, often filling narrow slot canyons like a bathtub. The tall, undulating walls have few exits for any hikers inside when the weather hits, quickly turning a casual hike into a dangerous situation.
In 2015, seven hikers died when a storm sent water rushing into a slot canyon in southern Utah's Zion National Park. Flood waters also killed a dozen people in a polygamous town on the Utah-Arizona border that year.