US President Donald Trump signed a major disaster declaration. The severe flooding left dozens of people dead and several others missing — many from Camp Mystic, a Christian youth camp.The death toll from flash floods in the US state of Texas jumped to at least 78 people on Sunday as the search for girls missing from Camp Mystic, a Christian youth camp, continues. Larry Leitha, the Kerr County Sheriff in Texas Hill Country, said the death toll in the hardest-hit Kerr County had reached 68, including 28 children. Ten more girls and a camp counselor are still unaccounted for. At least 10 others died from the floods in other Texas counties. Across the state, Texas Governor Greg Abbott said there were 41 people confirmed to be unaccounted for, and more could be missing. Abbott also warned that more rounds of heavy rain could fall on areas that are already affected. US President Donald Trump on Sunday issued a major disaster declaration for Kerr County. This is "to ensure that our brave first responders immediately have the resources they need," Trump posted on social media. What is the latest on the missing? Rescuers have been scouring the area to locate survivors, including 10 girls who have not been seen since the floods slammed into their camp, along the banks of the Guadalupe River. Around 750 girls were attending Camp Mystic, a Christian summer camp, in Kerr County, a rural area about 85 miles (140 kilometers) northwest of San Antonio. US media reported that four of the missing girls were dead, citing their families. Frantic parents and families posted photos of missing loved ones and pleas for information. The obituary section of a local news site featured tributes to victims, including Camp Mystic's owner and director Dick Eastland. The director of a nearby camp was also confirmed dead from the floods. Officials said more than 850 people had been rescued in the last 36 hours. However, many others had arrived in the area to celebrate United States Independence Day on Friday, so authorities say they don't know who else may be unaccounted for. Texas Department of Emergency Management chief Nim Kidd said air, ground and water-based crews were scouring the length of the Guadalupe River for survivors and the bodies. "We will continue the search until all those who are missing are found," he said. Dalton Rice, an official from the city of Kerrville, said rescuers were facing "very difficult" conditions while "looking in every possible location" for survivors. How did the floods unfold? The extreme weather began before daybreak Friday — the start of the Fourth of July holiday weekend — as months' worth of rain fell in a matter of hours. The fast-moving waters of the Guadalupe rose 26 feet (8 meters) in just 45 minutes, washing away homes and vehicles. Camp Mystic was overwhelmed by floodwaters that inundated its riverside facilities. Buildings were destroyed and the highway to the camp was washed away, hindering rescue efforts. Several other communities along the Guadalupe were hit hard, with buildings, bridges and roads washed out. Afterward, the National Weather Service said the flash flood had dumped more than a foot of rain, half of the total the region sees in a typical year. What questions are being asked? Officials and residents alike were shocked by the speed and intensity of the rising waters. The area along the Guadalupe River has long been vulnerable to flooding, sparking questions about the lack of proper warnings. The National Weather Service (NWS) had issued flood alerts, but US Homeland Security Secretary Kristi Noem said the warnings had not accurately predicted the extreme rainfall. Noem said the Trump administration was working to upgrade the early warning system, although the NWS's parent agency has recently faced huge cuts, leaving many weather offices understaffed. US Rep. Chip Roy, whose district includes the ravaged area, called it a once-in-a-century flood and acknowledged that there would be finger-pointing. The county had considered a river flood warning system similar to a tornado warning over the past decade, but officials say the cost was then deemed too high. Edited by: Kieran Burke