Since May, 30 large whales have died in the western Gulf of Alaska. Yesterday, the National Oceanic and Atmospheric Administration (NOAA) called the deaths an “unusual mortality event” and launched an investigationto figure out what is causing the whales’ demise, The Washington Post reports. So far, 11 fin whales, 14 humpback whales, one gray whale, and four unidentified species have perished in the area, bringing the large whale strandings for the region to almost three times the historical average, NOAA says. The causes of death are as yet unknown, although a leading hypothesis is harmful algal bloom toxins. Scientists report there has been no evidence so far of radiation exposure from the 2011 Fukushima nuclear disaster.