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Four people were found dead and three others were missing Tuesday in Zion National Park, one day after the group went into Keyhole Canyon as flash floods struck southwestern Utah.

The group of four men and three women from California and Nevada picked up their permit to go through the canyon about 7:30 a.m. on Monday, despite rangers' warnings that the flash flood danger was "probable," said park spokeswoman Aly Baltrus.

Some members of the group took a basic canyoneering course Monday morning before the group made its way into Keyhole Canyon — one of Zion's shorter technical canyons, Baltrus said. The route typically takes canyoneers about two hours, though advanced canyoneers have been known to complete the canyon in just 30 minutes, Baltrus said.

On Monday afternoon, a group of three canyoneers passed the victims at the first rappel, Baltrus said. As the group of three emerged from the canyon a short time later, heavy rains began to fall.

"They knew they were way ahead of the other group," Baltrus said. "They got out and notified [rangers] there was a group of seven possibly in there."

Rangers later found the group's unoccupied vehicles and began searching Tuesday morning, Baltrus said.

Park officials on Tuesday were not releasing the names of the seven canyoneers, pending family notifications.

Crews continued to search for the three missing canyoneers Tuesday, but searchers could not venture far into the canyon because of persistent flooding risks, Baltrus said. They have been calling into the canyon but have heard no response.

Monday's storm and resultant flash flooding is believed to be Utah's deadliest weather event. In addition to the deaths in Zion, 12 people were killed in nearby Hildale after Monday's floods swept away two cars occupied by women and children. A child who was in one of the cars was missing Tuesday night.

Investigators have tried to make contact with all of the people on the permit, in case any of them did not join the group in the canyon, Baltrus said. They were unable to locate any of the seven by phone or email.

The group of seven and the three canyoneers who preceded them were far from the only Zion visitors who claimed their canyoneering permits and made their way into the park's dramatic slot canyons despite Monday's high risk of flooding.

"We're still struggling to figure out how we can do better to get that message across," Baltrus said.

To descend Keyhole Canyon, canyoneers must complete several rappels of under 30 feet and swim through several pools, even when the weather is dry.

There are "a couple of places they may have been able to find a bit of high ground," Baltrus said, but once in the canyon, the only way out is to continue to the end of the route.

The watershed for Keyhole Canyon is 1.5 square miles — small for the slot canyons of southern Utah, Baltrus said. That means flash flooding likely occurred very soon after Monday afternoon's downpours.

In less than an hour Monday, 0.62 of an inch fell in Zion, Baltrus said. In one of the park's tributaries of the Virgin River, flows of 50 cubic feet per second swelled to more than 2,000 cubic feet per second in just 15 minutes, Baltrus said.

In Zion's canyons, those high waters have proved deadly time and again. In 2001, a flash flood washed away a 10-year-old boy on the Canyon Overlook trail. Two hikers were killed in a flash flood while they were exploring the Narrows in July 1998. In 1993, two adult leaders of a group of LDS Explorer Scouts from Salt Lake City died in a flash flood in Kolob Canyon. And in September 1961, four Boy Scouts and their leader were killed in a flash flood in September 1961 in the Virgin River Narrows.

Outside of Zion, a California husband and wife were killed on Sept. 11, 2008, when a torrent of water overtook them in the Egypt 3 slot canyon in the Grand Staircase-Escalante National Monument.

And in northern Arizona, a flash flood Aug. 12, 1997, in Antelope Canyon swept away a dozen hikers, killing 11 of them.