BOSTON (CBS) — An endangered sea turtle has died in part because she ate a large piece of plastic, the New England Aquarium said Saturday. The 420-pound leatherback sea turtle was found stranded on Cape Cod earlier this week.

The 11-inch by 5-inch piece of plastic was found during the necropsy but it was also clear that the female turtle had an entanglement injury, according to the aquarium.

New England Aquarium veterinarians and biologists work to save 420 pound endangered leatherback sea turtle that stranded on Cape Cod on Halloween morning (Photo Courtesy: New England Aquarium)

“The turtle had a major, gaping wound where its huge, right front flipper attached to the shell. The tissue in the area was clearly infected. To veteran staff, it was an all-too-familiar, entanglement injury caused by a wrap of rope around the flipper when sea turtles swim into vertical ropes that go down to fixed fishing gear or boat moorings,” the aquarium said.

Twelve leatherback sea turtles have been found entangled in rope off the coast of Massachusetts this year.