Researchers are scrambling to determine what’s behind the death of 30 whales in the Gulf of Alaska as unusually warm ocean temperatures continue to wreak havoc on the region.

Since May 2015, 14 fin whales, 11 humpback whales, one gray whale and four unidentified specimens have been found dead along shorelines in the Gulf of Alaska, nearly half of them in the Kodiak Archipelago. Other dead whales have been reported off the coast of British Columbia, including four humpbacks and one sperm whale.

This year’s total is roughly three times the annual average for the region, leading the National Oceanic and Atmospheric Administration to declare the deaths an “unusual mortality event.” The investigation into the deaths will take months, or even years, according to a statement released by the agency.

Predation, starvation, or disease could be behind the deaths, but researchers say there have been few signs of physical trauma to the whales. The more likely culprit is unusual water conditions.

Over the past two years, a large mass of warm water that climatologists have dubbed “the blob” has persisted in the north Pacific, and El Niño 2015 is pushing more warm water into the region.

The unusually warm and calm seas are believed to be behind a series of toxin-producing algae blooms – record-breaking in size and duration – stretching from southern California to the Aleutian Islands. Clams sampled near the town of Sand Point, Alaska were found to have toxin levels more than 80 times what the FDA says is safe for human consumption, said Bruce Wright, a scientist who studies toxic algal blooms for the Aleutian and Pribilof Islands Association. The levels were ten times anything Wright had previously recorded.

“The conditions I look for are warm water temperatures and sunny, calm weather,” Wright said. “All the conditions seem to be right for a significant event. And associated with this major event, you would expect to see die offs of marine mammals and seabirds and fish, and that’s what we’re seeing.”

The unusually warm water has been affecting sea and weather conditions in the North Pacific in other ways. Tropical fish have been turning up in Alaska, including four ocean sunfish – rare to the region – that were spotted in Prince William Sound earlier this month.

“I don’t think the ocean temperature would affect the whales directly,” said Bree Witteveen, a marine mammal specialist with the Alaska Sea Grant program in Kodiak. “It would be an indirect influence. It would alter where the prey is gathering — things like that.”

NOAA’s declaration that the whale deaths constitute an “unusual mortality event” triggers the formation of an investigative team and opens the possibility to secure additional funding for research, according to NOAA spokesperson Julie Speegle.

“We are sending up a team to investigate this particular event, and we’ll have more resources to hopefully get out and do more necropsies.” Speegle said. “The more samples we can take from these dead whales, we can test for biotoxins or viral agents and wide range of possible causes.”

Earlier this summer, Alaska Native communities along the coast, including Kodiak’s Sun’aq Tribe, had raised concerns about another possible danger to marine life — U.S. Navy training that allows the use of underwater sonar, which some research has linked to whale strandings.

“At this point, the tribe is just standing by to find out what NOAA comes up with,” said Tom Lance, natural resources director at the Sun’aq Tribe. “We’re not pointing fingers at the Navy. We’re suspicious that their activities could impact marine mammals, of course, but until we have more facts we can’t say definitively that it’s one thing or another.”

Only one whale has been sampled so far, and Wright said the carcass was too decomposed to provide any reliable insight.

“I really think we don’t have enough information to even speculate,” Witteveen said. “It’s definitely a mystery for us. I wish there was a smoking gun or leading hypothesis for us to look into. It’s just so unusual, it’s really hard to say.”