One of the State's largest milk suppliers, Avonmore, confirmed it has had a problem over the past week in Dublin with some of its milk products going sour before their sell-by date.
The problem did not pose a health risk and did not necessitate the withdrawal from sale of any product, a spokesman for Glanbia - Avonmore's owners - said.
The company had received "a small number of complaints" in recent days from the public about milk going off, the spokesman added.
After detailed checking, the problem was being attributed to "a long summer and high humidity".
This, he admitted, was causing inconvenience for customers but was not harmful.
"It relates to the milk maturing process happening earlier than usual," the spokesman said.
Such problems often occurred during the high summer season, he said, but not usually at this time of year.
While he was not in a position to quantify the number of calls received at Avonmore's Belgard Road offices, he denied it was a large number.
Quality control staff were monitoring the problem and were contacting distributors to alert them to be "extra vigilant", the spokesman said.
Avonmore's milk for the Dublin market is collected for processing at its facilities in Ballitore, Co Kildare, and Drogheda, Co Louth, before being transported to depots in the capital for distribution.
