Southwest Airlines says a child was hurt by a support dog as passengers boarded a plane in Phoenix.
A passenger tweeted that the dog bit the girl as she approached and that she screamed and cried.
Southwest said Thursday that the dog's teeth "scraped a child's forehead" and that paramedics checked the child, who was not identified.
The child stayed on Wednesday's flight to Portland, Oregon, while the dog and its owner stayed behind. Southwest said it could not confirm the child's age.
The incident came as Delta and United airlines prepare to crack down on emotional-support animals on planes.
Unlike service animals such as guide dogs, support animals need no training. However, passengers can be asked to show a medical professional's note explaining why support animals should travel.