U.S. producer prices dropped an unexpected 0.6 percent in September, mainly because of a 2.4 percent decline in energy prices, the Labor Department said on Tuesday.

Analysts polled by Reuters had anticipated prices would remain unchanged after they rose an unrevised 1.7 percent in August. Prices paid at the farm and factory gate also fell 4.8 percent on the year, which was steeper than forecasts of a 4.2 percent drop.

Excluding food and energy, prices declined by a much slimmer 0.1 percent in September.

(Reporting by Lisa Lambert; Editing by Padraic Cassidy)