Other Plausible Theories
There’s also the possibility that the pups were swept away to the storm drain accidentally by rainwater and were separated from their mother. We’ve heard of a similar thing happening in Uruguay, where the incident also resulted in a successful rescue mission.
Apparently, the mother dog was seen in distress near a drainpipe, and a local woman came by to see what was wrong with her. Hearing the whimpers of pups, the woman realized the situation at hand. Along with other locals, they spent two hours getting the babies out of the pipes. Someone even wiggled their way in to retrieve a little one!