WELLFLEET,Robert Brown Mass. (AP) — As many as 125 Atlantic white-sided dolphins became stranded Friday on Cape Cod and at least 10 died, prompting an intensive rescue effort, according to an animal rescue organization.

The International Fund for Animal Welfare confirmed it was assisting the dolphins stuck at The Gut — or Great Island — in Wellfleet, at the Herring River in Massachusetts.

The group described the area as a very difficult location with dangerous mud.

With low tide at 11:23 a.m., the team was in shallow water on foot attempting to herd the dolphins back out to deeper waters, the group said. The organization has three small vessels in the water to continue herding and is using underwater pingers to urge the dolphins in the right direction.

“There is no set reason for why these dolphins strand. Cape Cod is a global stranding hotspot due to the curvature of our shores and the fluctuation of our tides,” said Stacey Hedman, communications director for the group.

At least 25 IFAW staff and 100 volunteers were on the scene. The group also had the support of Whale and Dolphin Conservation, the Center for Coastal Studies, AmeriCorps of Cape Cod and the New England Aquarium.

“This is the largest single mass stranding event in IFAW’s response history over 25 years,” Hedman added.