The largest influence in the drop was gasoline prices, the data agency said.
Gasoline prices dropped 6 percent on a year-over-year basis in April after sliding 0.3 percent in March.
The decline in gasoline prices was the largest on an annual basis since October 2009.
Excluding gasoline prices, the consumer price index rose 0.8 percent in the 12 months to April following a 1.1 percent increase in March.
Consumers, meanwhile, paid more for food and shelter. Prices for food rose 1.5 percent on an annual basis in April following a climb of 1.8 percent in March.
The cost of shelter rose 1.3 percent in the same period following a 1.1 percent rise in March.
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