A probe is under way to determine the cause of the deaths.
Massive deaths of this kind occur on an almost yearly basis in the Caspian region.
Environmentalists blame the frequency of such incidents on nearby oil fields.
Caspian Energy Special
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HOW MUCH OIL? The U.S. Energy Information Administration has estimated that the Caspian could hold between 17 billion and 33 billion barrels of proven oil. ("Proven reserves" are defined by energy experts to be 90 percent probable.) Other experts estimate the Caspian could hold "possible reserves" of up to 233 billion barrels of oil. ("Possible reserves" are considered to be 50 percent probable.) By comparison, Saudi Arabia has 261 billion barrels of oil and the United States 23 billion...(more)