KENNEBUNKPORT — The Coast Guard says cleanup is underway following the discovery of an oil spill on an island that’s part of Cape Porpoise.

The Coast Guard says it received the initial report of an oil sheen and oil on the coast of Bickford Island on Sunday.

Clean Harbors, an environmental cleanup company, was on the scene Monday morning, along with local officials and the Maine Department of Environmental Protection.

Cape Porpoise is part of Kennebunkport, and the island has homes and several restaurants.

The Coast Guard says it’s trying to determine the source of the spill. Lt. Cmdr. Timm Balunis says one of the theories is that a boat pumped its bilge near the island, fouling 100 to 150 yards of shoreline. He says tests were being taken.