U.S. wholesale prices unexpectedly sank in September.
The producer price index dropped 0.3%.
That's the steepest decline since January.
Economists had been expecting a slight increase.
Weighing on that index: gasoline prices.
They fell sharply in September, dragging down wholesale energy prices.
A drop in the cost of trade services was another factor.
On a 12-month basis, the PPI rose 1.4%.
That's the smallest increase in nearly three years.
The weak readings come amid a backdrop of a slowing economy, trade tensions with China, and cooling growth overseas.
The data is a disappointment for officials at the Federal Reserve, who have set an annual inflation target of 2%.
The PPI data could give the central bank room to cut interest rates again later this month.
The Fed cut rates last month to keep the economic expansion on track.
The weak inflation data sent Treasury yields south.
The markets get their read of inflation at the retail level when the consumer price index comes out on Thursday.