Rescue workers patrolled by foot and by airboat in the search for those still missing from flash floods that swept Texas over the July Fourth weekend.

Across Central Texas, there have been more than 90 confirmed deaths from the weekend flooding: six people were reported dead in Kendall County, seven in Travis County, four in Williamson County and four in Burnet County, officials said Monday. At least 15 people are still missing in the Austin area.

Survivors have described the floods along the Guadalupe River as a “pitch black wall of death” and said they received no emergency warnings.