Flash flooding in Texas Hill Country has triggered one of the largest rescue operations in the state’s history.

Rescuers searched the Guadalupe River for survivors of the Texas flash floods that killed at least 95 people over the July Fourth holiday weekend, with an unknown number of people still missing. The basin area was crowded with families and campers preparing to enjoy the holiday when pounding rain brought about catastrophic flash floods just before dawn Friday.

This is the first solid number officials have provided regarding campers who remain unaccounted for, after estimating Saturday that it could be as high as 27. There were about 750 children at Camp Mystic when the floods hit,