In the wake of catastrophic flooding in Central Texas that left more than 125 people dead and dozens missing, federal and state officials have warned residents and donors about a surge in disaster-related scams designed to exploit vulnerable families and charitable givers.

The homeland security secretary said a report that thousands of calls to a disaster hotline went unanswered because of staffing cuts was “false.”

The Homeland Security chief denied that a memo she issued in June requiring her to approve FEMA expenditures over $100,000 caused the agency to move more slowly.