Transcript for Scientists Puzzled By Dolphin's Deadly Summer
tonight, here, the alarming discovery up and down of the east coast, the dolphins found dead. Scientists working feverishly trying to figure out why. Abc's gio benitez on the new clues. Reporter: The images are difficult to look at. Bottlenose dolphins mysteriously turning up dead along the east coast. Scientists are baffled and alarmed. We don't know what's causing this at this point. Reporter: Nearly 120 have washed up along the east coast. From new york, down to virginia, where in just that state alone, 64 dolphins have been found in about a month's time. And scientists say anything could be to blame. From biotoxins, to disease, even human interaction. Anytime you have a pulse of strandings like this, it's definitely a cause for concern. There's no indication that this is a water quality issue. All indications are pointing to this being just a natural disease cycle in dolphins. Reporter: It's happened before. IN THE LATE '80s, 750 DOLPHINS Were found dead along the east coast. The cause -- a virus. Scientists say some of the new corpses in new jersey tested positive for that same virus. A marine version of the measles, eventually leading to a deadly pneumonia. But some experts insist disease is just one piece of the puzzle. It's still way too early in the game to start speculating on the cause of this event or how long it will take place. Reporter: And tonight, experts are rushing to find answers, but point out that many of the dolphins are turning up dead in areas with heavy human footprints.
This transcript has been automatically generated and may not be 100% accurate.