PORTLAND, Maine (AP) — Government scientists launched an investigation Thursday into an unusually large number of humpback whale deaths from North Carolina to Maine, the first such "unusual mortality event" declaration in a decade.

Forty-one whales have died in the region in 2016 and so far in 2017, far exceeding the average of about 14 per year, said Deborah Fauquier, a veterinary medical officer with National Oceanic and Atmospheric Administration Marine Fisheries.

Ten of the 20 whales that have been examined so far were killed by collisions with boats, something scientists are currently at...