BANDON, Ore. (AP) — Officials say an endangered species of whale that became stranded on a southern Oregon beach died over the weekend. The Oregonian/OregonLive reports the 38-foot (12 meter) sei whale died Saturday evening after it was stranded on the sand by the tide. Marine mammal biologists say the sei whale was not yet mature. The species prefers to live in temperate waters in the mid-latitudes. Officials said a necropsy would be done to learn why the animal got stranded. The whales are endangered in the U.S. According to the National Oceanic and Atmospheric Administration, there are about 8,600 sei whales in the North Pacific — 20% of the 42,000 that used to live in those waters.