ANCHORAGE, Alaska (AP) — Two environmental groups say cold-water corals discovered near a proposed Shell Oil drilling site in the Chukchi Sea deserve additional review, but the company contends they have been studied and are not threatened.

Greenpeace USA and the Center for Biological Diversity in a letter Thursday called on Interior Secretary Ken Salazar to block drilling until the department conducts a supplemental environmental review of potential damage to the corals.