Two juvenile humpback whales washed up on a Cape Cod island this week, and experts aren't sure why. 

By the time rescuers got to a stranded whale on Monomoy Island off Chatham on Wednesday, it had already died. As they were struggling in the surf to get a necropsy, they got word of another beached humpback about two miles away. That one was in such bad shape that it had to be euthanized.

Brian Sharp of the International Fund for Animal Welfare said it’s been several years since they've seen a whale stranding. “They are rare in any one given area, so to have two happen within two miles, that was unheard of in our area,” he said.

Federal officials recently started an investigation into deaths like this.

“There has been an increase in dead humpback sightings from North Carolina through the Northeast region over the last year," Sharp said. "So samples from these animals will go towards that investigation.”

Sharp said they don't know if the whales got caught in a shallow tide or had some health problem that caused the strandings. 

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A humpback whale stranded on Monomoy Island
Courtesy of the International Fund for Animal Welfare