BEIJING, Oct. 15 (Xinhua) -- China's producer price index (PPI), which measures costs for goods at the factory gate, dropped 1.2 percent year on year in September, the National Bureau of Statistics (NBS) said Tuesday.

The reading expanded from the 0.8-percent decline in August, the NBS data showed.

On a monthly basis, the PPI rose 0.1 percent last month, bucking the trend of the 0.1-percent drop in August, according to the NBS.

In the first nine months, the PPI on average was unchanged from that in the same period of last year.

Factory prices of production materials decreased 2 percent year on year in September, expanding from the 1.3-percent decline in August.

Among major industries, oil and natural gas extraction saw faster price drops in September, declining 13.4 percent year on year, according to the NBS.

Prices for ferrous metal mining and dressing rose 15.7 percent over one year ago, while non-ferrous metals mining and dressing saw producer prices rise 5.7 percent year on year in September.

Eighteen among 40 surveyed industries saw price hikes month on month, while 11 reported price drops and 11 witnessed unchanged prices.

NBS senior statistician Shen Yun said the carryover effect of last year resulted in a drop of 0.7 percentage points in the PPI decline in September, while new factors dragged down the index by 0.5 percentage points.

Tuesday's data also showed China's consumer price index, a main gauge of inflation, rose 3 percent year on year in September.