Officials in Central Texas are desperately searching for survivors after a flash flood on Friday left at least 78 people dead and dozens unaccounted for, including many children. More than 850 people have been rescued so far — many by helicopters, officials said. Of the dead, 68 of the them were in Kerr County, officials said at a Sunday afternoon news conference. The death toll in the county includes 40 adults and 28 children, Sheriff Larry L. Leitha said. In addition to the deaths in Kerr County, 10 others died due to flooding in surrounding counties, according to officials. Meanwhile, the search continues for 10 girls and a counselor missing from Camp Mystic, a Christian summer camp next to the Guadalupe River, Leitha said. W. Nim Kidd, chief of the Texas Division of Emergency Management, said officials are still holding out hope and are "very much fueled by the compassion that we feel for these families." "We're doing everything we can to find their missing loved ones," he said. More than 400 first responders from over 20 agencies in Kerr County were assisting with the search and rescue, Leitha said earlier Sunday. In addition, more than 100 vehicles and some dozen K-9 units were scouring the area around the Guadalupe River in search of survivors, according to the Kerr County Sheriff's Office. More than 1,000 personnel are assisting in search-and-rescue operations, according to the Texas Division of Emergency Management. The search area has been expanded from Kerr County to include San Saba and Burnet counties, which were also affected by the flooding, officials said Sunday. Although first responders have faced challenges such as heat, snakes and impassable roads due to flooding and debris, debris removal was still underway and improving, officials said Sunday. The officials are also cautioning residents not to fly drones in the search areas, including along the Guadalupe River, because it is hampering search drones from agencies. More rainfall ahead Flash flood warnings were issued for Central Kerr County until 7:30 p.m. Parts of the Hill Country were under a flash flood watch until 7 p.m., according to the National Weather Service office in Austin/San Antonio. The ground in the areas that flooded remains saturated and even "a little bit of rain, rainfall and watershed can cause issues," according to Texas Department of Public Safety Director Col. Freeman F. Martin, who spoke on Sunday. An emergency alert phone message was sent out Sunday afternoon to area residents telling them to seek higher ground because of "high confidence of river flooding at North Fork of river." Texas Gov. Greg Abbott on Sunday warned residents to be "extraordinarily cautious" for the next 24-48 hours and avoid driving on flooded roads. He said people had died when they were swept away in vehicles and warned residents that water on roads could rise very rapidly. "You may think you can drive through it, only to find out when you're in there that it's too late and that you're getting swept away," Abbott said. "If there's any water on the road, you gotta be safe. There's an old saying for a reason... 'turn around, don't drown'."