Rescue workers patrolled by foot and by airboat in the search for those still missing from flash floods that struck this part of Texas over the July Fourth weekend, leaving more than 100 confirmed dead.

A July Fourth weekend deluge in Texas caused catastrophic flash flooding that has killed at least 89 people. Camp Mystic in Kerr County says Monday morning that it is “grieving the loss” of 27 campers and counselors as the search continues for victims of the disaster.

Search teams plodded through mud-laden riverbanks and flew aircraft over the flood-stricken landscape of central Texas for a fourth day on Monday, looking for dozens of people still missing from a disaster that has claimed at least 78 lives.