Dolphins, by the hundreds, are dying off the coast of Peru. And the reason for their death seems to be big mystery.

About 877 dolphin carcasses have been found along the shores of the country’s northern regions, said Deputy Environment Minister Gabriel Quijandria. It has set off alarms in Peru, with investigators trying to determine why they are dying.

Among the possible facots are a virus or seismic oil exploration that has recently been carried out off northern Peru.

An analysis of the beached dolphins' internal organs hasn't found the sort of symptoms that experts have seen in other cases when dolphins have been affected by seismic tests, Quijandria said in a radio interview.

He said experts are studying whether the animals could have succumbed to a virus. "So far, it's the most probable hypothesis, and it isn't the first time it's happened. There have been cases in Peru, in Mexico, the United States," Quijandria said.

He said the seismic tests produce underwater noise that can harm dolphins. But he also said that in Peru it's the first time such dolphin deaths have coincided with seismic work and that the dolphins began dying before the tests started.

Carlos Yaipen, who leads the non-governmental organization Orca, said the beached dolphins began appearing in January. Dolphins have had broken bones in their ears and some of their organs have been collapsed, suggesting that shock waves generated by the seismic tests could have killed them, Yaipen said.

However, Patricia Majluf, the government's deputy fisheries minister, said that based on the available evidence officials haven't been able to pin down any relationship to oil exploration.

Government officials have said scientists are carrying out further studies that they expect to finish in about two weeks.

Based on reporting by The Associated Press.

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