"According to bystanders, there was another seal pup nearby which had a fishing hook removed from its mouth by onlookers earlier on in the day," Waitoa said.
Waitoa said officers couldn't confirm the allegations.
During the winter period (March 2 to November 30), dogs are allowed off the lead during the hours of 2pm to 10am.
However under alert level 2, Waitoa said it's encouraging dog owners to keep their pets on a leash at all times.
Animal Management have increased patrols in the area, however they have had no other reports of dogs attacking seals at the Auckland beach.
The Department of Conservation says if you encounter a seal on or near a beach, give it space:
• Always keep dogs on a leash, under control and away from seals
• Ensure you keep small children at a safe distance and under your control when watching seals
• Don't get closer than 20 metres
• Do not get between the seal and the sea
• Do not touch or feed the seal
Animal Management notified DoC so an investigation into the incident could begin.
DoC has been contacted for comment.