The authorities confirmed that 20 girls were still missing as a result of the flooding along the Guadalupe River, but the full scope of the disaster was not clear.

Several people were killed and others unaccounted for after heavy rain caused flooding along the Guadalupe River.CreditCredit…The New York Times

At least 13 people were killed and frantic searches were underway for the missing — many of them children — after heavy rain in Central Texas set off deadly flooding along the Guadalupe River on Friday, the authorities said.

Lt. Gov. Dan Patrick told reporters at an afternoon news conference that at least 20 girls from a summer camp along the river in Hunt, Texas, were missing after catastrophic flooding overnight.

Lisa Walter, a spokeswoman for Kerr County, northwest of San Antonio, said the number of fatalities confirmed Friday would grow. She declined to disclose further details until the victims’ relatives could be notified.

“Keep in mind, this event is only hours old,” she said. “It is still a very active, ever-changing situation.”

The Kerr County Sheriff’s Office encouraged residents “to shelter in place and not attempt travel. Those near creeks, streams and the Guadalupe River should immediately move to higher ground.”

The scope of the disaster was not immediately clear, but Texans on Friday were bracing for the worst. Camp Mystic, which has multiple campsites along the river, said it was working with search and rescue teams but was struggling to get more help to campers since the nearby highway had washed away.

Here is what else to know:

• Regional flooding: Throughout the region, torrential downpours prompted evacuation orders and water rescues as the churning river burst from its banks, rising at an alarming rate from seven feet at midnight in Hunt, Texas, to over 29 feet at 4 a.m., according to the National Oceanic and Atmospheric Administration.
• Kerrville: The police said on social media that they were working with the Kerrville Fire Department to evacuate residents, noting that “many roads and streets are flooding in town. A Walmart store was being used as “a temporary reunification center” for people who had been displaced by the flooding, the Police Department said.
• San Angelo: The Weather Service in San Angelo, Texas, said it had “received multiple reports of flooded roads and homes across Tom Green County.” “These conditions are life-threatening,” the agency said, warning people stay off the roads if possible.