FLAGSTAFF, Ariz. (AP) — A first-of-its-kind federal study of Native American boarding schools that for over a century sought to assimilate Indigenous children into white society has identified more than 500 student deaths at the institutions so far. But officials say that figure could grow exponentially as research continues. The Interior Department report released Wednesday expands to more than 400 the number of schools that were known to have operated across the U.S. for 150 years, starting in the early 19th century. It identified more than 500 deaths in records for about 20 of them. The agency says a second volume of the report will cover burial sites and the impacts of the boarding schools on Indigenous communities.