In the latest development in an uncanny trend of mass dolphin and marine mammal deaths, over 400 dead dolphins were discovered on the Pacific beaches of northern Peru last month, the Associated Press reports Tuesday.

Scientists said over 220 were found in the last week of January alone.

Autopsy results were expected in the next two weeks, but suspicions range from "biotoxins in the sea to seismic testing or an unknown ailment," the AP reports.

Over 870 dolphins were found dead along Peru's beaches in 2012, but scientists have been unable to trace a definite cause of these mass die-offs.

As Common Dreams has reported, in 2013 eight times the historical average amount of dolphins washed up on U.S. East Coast shores from New Jersey to Florida.

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