Federal government investigating Alaska whale deaths

 (CNN)Whales are dying at an alarming rate in the western Gulf of Alaska, and federal investigators say they’re determined to find out why.

At least 30 large whales have died in Alaska since May, the National Oceanic and Atmospheric Administration said this week in declaring the first “unusual mortality event” for large whales ever declared in the state.

Authorities in the Canadian province of British Columbia have also reported unusual whale deaths, and officials in Alaska have also noted widespread deaths of common murres, a species of bird, along the Alaska Peninsula, NOAA said.

Bears are seen feeding on a carcass of a fin whale in Larson Bay, Alaska, in this image provided by NOAA.

Fewer than 15 large whale strandings have been reported in the area each year since 2010, according to NOAA.

What’s causing the deaths is unknown, the agency said.

Samples are being collected to test for bacteria, viruses and biotoxins like algae that might be responsible, the agency said.

“Biotoxins will be one of the top priorities, but not the only priority that we’ll be looking at to rule in or rule out whether it’s playing a role in this death investigation and these mortalities, both in Canada and the U.S.,” said NOAA Fisheries scientist Teri Rowles to the Alaska Daily News.

So far, the corpse of only one Alaska whale has been tested and most of the carcasses have been floating and couldn’t be retrieved, the agency said.

Results of the investigation could take months or even years, they said..

The die-off comes amid a major algae bloom that stretches from central California north to Washington, according to NOAA. Waters off Alaska could also be impacted, the agency said.

Unusual mortality events involve an increase in the number or tempo of marine mammal deaths or deaths involving vulnerable species or other conditions suggesting something unusual is causing the deaths.

Since 1991, NOAA has recorded 61 such events. Nearly half have ultimately been traced to infections, biotoxins, human interactions or malnutrition. Biotoxins from algae blooms are responsible for the majority of recent declarations, according to NOAA.