Official figures show that factory gate prices - the price of goods before they reach the consumer - fell by 0.4% in August compared with July.
This left factory prices 1% lower compared with August last year.
The biggest increases in the month were in fish and fish products, up 1.9%, and electrical equipment prices, which were 1.4% higher.
There was a 1.1% fall in the other food products category - which includes bread and confectionery.
Prices of building and construction materials rose 0.6% in August, giving a 2% annual increase. In this sector, prices of copper pipes and fittings have jumped almost 26% in the last 12 months.
Energy product prices fell 1.3% in the month, with petrol fuels falling 3.7%. Energy prices are still 3.3% ahead over 12 months, however, with petrol fuel prices up 9.1%.
