More than 300 search-and-rescue dogs worked at Ground Zero following the Sept. 11, 2001, attacks, helping locate survivors and human remains amid the destruction.

NYPD K-9 handler Robert Schnelle and his dog, Atlas, worked 12-hour shifts for more than eight months. Veterinarian Dr. Cynthia Otto said the dogs also provided comfort to first responders during the recovery.

Research later found that the dogs generally faced few long-term health risks, while handlers who worked alongside them showed lower rates of PTSD. Their courage and loyalty remain an enduring part of the 9/11 story.

abcnews.com