How did police K-9 not pick up on any/all of the children's scent?

Loved the movie thought it was great. Police dogs/bloodhounds are amazing and can track missing persons for MILES and some have even picked up trails that are a week old. I've seen theories saying the witch and her magic had a part to play with the police incompetence and how they handled the case. Although, this seems like a significant plot hole to me that none of the police dogs could pick up a scent. Is there an explanation to this that I've missed?