The U.S. government is launching an investigation into the recent deaths of endangered North Atlantic right whales.
At least 13 of the whales have been found dead this year off the coasts of Canada and New England.
An arm of the National Oceanic and Atmospheric Administration said Thursday it is declaring the deaths “an unusual mortality event.”
The agency says that designation triggers a “focused, expert investigation” into the cause of the deaths.
Representatives from Fisheries and Oceans Canada and NOAA Fisheries are expected to provide more information about the investigation Friday morning.
Some of the whales have died due to ship strikes or fishing gear entanglement.
No more than 500 of them still exist in the wild.
Conservation groups and marine scientists have said the high number of accidental deaths this year threaten the survival of the species.
The right whales, which summer off of New England and Canada, are among the most imperilled marine mammals on Earth as populations have only slightly rebounded from the whaling era, when they nearly became extinct.
Fisheries and Oceans Canada is using a host of new methods to try to help the whales, including surveillance flights along the Gulf of St. Lawrence coastline and new speed restrictions for ships.