(NewsNation) — The Kerr County sheriff in Texas reported on Friday night that flash floods had resulted in at least two dozen fatalities, while a similar number of young campers were still missing after heavy rains caused the Guadalupe River to overflow.

“At this moment, we can confirm approximately 24 deaths,” Sheriff Larry Leitha stated at a news briefing with Texas Governor Greg Abbott. “We won’t be releasing any names just yet as we are still notifying the next of kin.”

He mentioned that between 23 and 25 girls from Camp Mystic, who had been camping near the river, were still unaccounted for. The Central Texas river received several months’ worth of rain within just two hours, causing its water level to rise by more than 20 feet overnight.

Officials said 237 people had been rescued so far, including 167 by helicopter. Abbott, who issued a disaster declaration for 15 counties affected by the flooding, said a variety of state personnel and resources would continue to assist local authorities in finding the missing.

“We remain in a search-and-rescue posture right now,” the governor said. The missions, Abbott added, “will continue in the darkness of night. They will be taking place when the sun rises in the morning. They will be nonstop, seeking to find everybody who is unaccounted for.”

Girls from camp unaccounted for

The region is home to many summer camps, but officials said they were able to account for children at all of the other places.

NewsNation national security contributor Tracy Walder, whose daughter is friends with some of the missing girls from Camp Mystic, said the relay of information has been a challenge because campers did not have access to technology during their stay.

“Technology is actually not allowed there,” Walder said. “That’s why communication and information is kind of a bit difficult to come by at this point in time.”

President Donald Trump has been in touch multiple times, Lt. Gov. Dan Patrick said, with offers to provide assistance.

By Friday morning, the Guadalupe River in western Kerr County had reached 29 feet, the second-highest level on record.

The river surpassed flooding levels seen in 1987, when floods killed 10 teenagers near Comfort, Texas.

Officials in Comfort issued an order for mandatory evacuations Friday for residents along the river and in Kerrville as police and firefighters helped get people to safety.

In San Angelo, Texas, photos showed a flooded intersection where water reached the level of street signs, and the weather service office there called the floods life-threatening.

Texas officials activated the National Guard and deployed the state’s Department of Public Safety and other resources to the area to respond to the flooding.

Kerr County Judge Rob Kelly told media outlets that there was no warning regarding the severity of the flood and said the county doesn’t have a warning system.

The National Weather Service had placed the county under a flood watch Thursday night, with a flash flood warning issued around 1 a.m. A variety of officials, however, said they were caught off-guard by the dramatic scope of the event.

The Associated Press contributed to this report.