Federal scientists say a massive die-off is taking place on a coral reef of a national marine sanctuary in the Gulf of Mexico.

Steve Gittings, chief scientist with the Office of National Marine Sanctuaries, reported this week that federal scientists reported a large-scale mortality event of unknown cause was taking place at the East Flower Garden Bank in Gulf of Mexico.

The reef is part of the Flower Garden Banks National Marine Sanctuary, which is about 100 miles off the coasts of Louisiana and Texas.

Gittings says researchers are reporting unprecedented numbers of dying corals, sponges, sea urchins, brittle stars, clams and other invertebrates.

Gittings says sport divers discovered dead animals on Monday and alerted nearby federal scientists who were doing annual monitoring work on the same reef.