The grueling, desperate search for 27 missing girls stretched into a third day on Sunday after raging floodwaters surged into a summer camp as rescuers maneuvered through challenging terrain, while Texans were asked to pray that any survivors would be found.

At least 51 people, including 15 children, were killed, with most of the deaths coming in Kerr County in the state’s Hill Country. Besides the 43 dead in Kerr County, four deaths were reported in Travis, three in Burnet and 1 in Kendall.

Rescuers dealt with broken trees, overturned cars and muck-filled debris in a difficult task to find survivors. Authorities still have not said how many people were missing beyond the children from Camp Mystic, a Christian summer camp along the Guadalupe River in Kerr County where most of the dead were recovered.

With each passing hour, the outlook became more bleak. Volunteers and some families of the missing who drove to the disaster zone began searching the riverbanks despite being asked not to do so.

Authorities faced growing questions about whether enough warnings were issued in area long vulnerable to flooding and whether enough preparations were made.