A surge in gas costs drove wholesale prices up in September by the most in five months. Economists cautioned that much of the increase was the result of one-time factors and said broader inflation remains modest.
The Producer Price Index, which measures price changes before they reach the consumer, rose 0.8 percent in September. Energy prices climbed 2.3 percent. Wholesale gas prices jumped by the most since March.
Excluding energy prices, wholesale prices rose just 0.3 percent.
Food prices also rose sharply. The costs of beef, veal and vegetables all increased.
Excluding food and energy costs, which tend to fluctuate sharply from month to month, so-called core prices increased a modest 0.2 percent. Higher prices for pickup trucks accounted for one-third of the increase in core prices.
Economists said seasonal adjustments magnified the rise in energy costs. Gas prices usually start to decline in September, when the summer driving season ends. Instead, wholesale gas prices rose during the first half of the month, when the survey was taken.
Gas prices later fell in the second half of September, economists said.
Neil Dutta, an economist at Bank of America, attributed much of the gain in wholesale prices to one-time factors. In addition to the spike in energy prices, he said the 0.6 percent rise in the cost of pickup trucks may have been part due to lingering supply chain disruptions caused by the March earthquake in Japan.
"Is this a harbinger of broad-based inflation that is about to hit the U.S. consumer?" he asked. "Don't count it."
Wholesale gas prices surged 4.2 percent, the biggest jump since March. The cost of diesel fuel and liquefied petroleum gas also rose. Natural gas prices dipped.
Wholesale prices had moderated in recent months, after rising sharply earlier this year. Fears of a possible recession in the U.S. and slower growth overseas had restrained inflation.
The price of commodities, such as oil and grains, generally fall when growth slows because that reduces demand. It can take several months for lower prices to reach the consumer.
The core index has risen 2.5 percent in the twelve months that ended in September, the same as the previous month.
"Inflation is not wildly out of control but it certainly isn't as tame as would be expected during this stage," said Jennifer Lee, a senior economist at BMO Capital Markets.
Before September, wholesale energy prices had fallen for three straight months, dragged down by lower oil prices.
The price of oil hovered around $86 per barrel in Tuesday trading. That's down 24 percent from a recent peak in May. That's helped reduce gas prices, which averaged $3.47 per gallon on Tuesday, according to AAA. Gas prices have moved up in recent days but are down from $3.59 per gallon a month ago and nearly $4 per gallon in May.
Wholesale food prices rose 0.6 percent in September after a sharp increase in August.
That trend could cool next year. The U.S. Department of Agriculture reported last week that farmers will likely finish next summer with a bigger surplus of corn than previously expected. A bushel of corn cost $6.41 Monday, down from a record $7.99 in June.
Tuesday's report could make it more difficult for the Federal Reserve to take aggressive steps to boost growth. That's because it shows prices of some goods are still rising. The central bank last month said it would swap $400 billion of its short-term Treasury securities for longer-term securities in an effort to lower long-term interest rates.
Some Fed policymakers supported more aggressive steps, according to minutes of September's meeting, released last week. But three policymakers dissented out of concern that the Fed's efforts could spur inflation.
The Fed's informal inflation target is about 1.5 percent to 2 percent growth in core prices, at an annual rate. Last month, Fed policymakers said that inflation would decline to levels "at or below" the target, according to minutes released last week.
A small amount of inflation is good for the economy. It encourages businesses and consumers to spend and invest money sooner rather than later, before inflation erodes its value.