WASHINGTON (Reuters) - The U.S. Environmental Protection Agency has waived federal requirements for some gasoline blends in eight southern states to help prevent supply constraints after Hurricane Isaac hit the Gulf Coast last week.

The agency said the storm caused an "extreme and unusual fuel supply circumstance" that justified easing fuel requirements in those states through September 15.

(Reporting by Ayesha Rascoe; Editing by Gerald E. McCormick)