New figures from the Central Statistics Office show a 2.3% fall in monthly factory gate prices in September.
This compares to a rise of 1.2% the same time last year, and resulted in an annual change of 2.2% in the year to September compared to an increase of 6% in the year to August.
The most significant price changes seen last month were in dairy products, which rose by 3%, while grain milling and animal feeds increased by 0.7%.
Computer, electronic and optical product prices fell by 4.1% while other food products - including bread and sweets - fell 3%. There was also a 2.9% fall in the price of basic pharmaceutical products.
Today's figures show that the price of energy products rose by 3.3% in the year since September, while petroleum fuels increased by 8.4%. During the month of September, the monthly price index for energy products inched 0.1% higher while petroleum fuels increased by 0.2%.
