The UK Food Standards Agency (FSA) said in a statement on Monday afternoon: "At this stage, there is no reason to believe that milk production will be affected, particularly as dairy herds are mainly kept indoors at this time of year and would not be grazing outside."
It added that risk to food crops, including vegetables and fruit, was no "immediate concern".
The reassurance came as fire fighters began getting to grips with the fire at Buncefield fuel depot in Hemel Hempstead. Crews were using 32,000 litres of water per minute.
Several explosions, which began early on Sunday, caused what some have called the biggest peace-time blaze in Western Euorpe and have left a thick cloud of black smoke spreading across parts of southern England.
No one was killed but 42 were injured, and some seriously.
Christian Fox, chairman of the UK Dairy Council, said milk supplies were not under threat and cows' feed "is a mixture of silage and hay harvested in the summer, together with other bought-in elements to keep them in the best possible condition.
"They will certainly not be consuming grass grazed outside."
UK deputy prime minister John Prescott said in Parliament on Monday afternoon: "I can't give an effective answer as to whether milk production will cease at this point," adding it was too early to predict.
The Dairy Council and the FSA are monitoring the situation for signs of any long-term damage to pasture lands.
A more pressing issue for the food sector is the prospect of more fuel price rises or even shortages resulting from the depot fire.
The government has warned of possible short-term local shortages but said there should be no great problem in the long-term.
Prescott praised emergency services and said in Parliament Monday afternoon that there was no need for panic petrol buying.
He said the industry has assured that "any lessons to be learned from this will be passed on", amid calls for an inquiry into where fuel depots are situated.