Jersey Dairy, which recalled the packs of semi-skimmed milk last week, said it suspected the source of the problem had come from "routine maintenance of the building".
Independent tests have since shown the bacteria found in the milk, known as Leclercia Adecarboxylata, was not considered a danger to human health.
Jersey Dairy, which recouped most of the milk within 24 hours of the recall, said it had double checked all storage tanks and production lines, as well as sterilisation tanks and cleaning procedures. No problems have occured with milk since the recall.
Kevin Keen, the firm's managing director, paid tribute to the group's in-house laboratory for enabling it to deal efficiently with the problem.
"It proves to us once again that whilst dedicated laboratory and quality management systems are not a compulsory requirement for the operation of a dairy, they should be and it is something we just would not do without, no matter what the pressure on cost."
Jersery Dairy's lab employs three permanent staff and carries out 27 separate tests on the firm's milk from the farm gate right up to the end of its shelf life, in addition to numerous tests on processing equipment, the group said.
Keen again apologised to consumers for the contamination of the semi-skimmed milk.
The problem threatened to add to a dispute over dairy hygiene practices in the EU, following allegations by the European Commission that UK food safety authorities were not doing enough to protect the public from potentially contaminated milk.
Jersey is a British crown dependency. It is responsible for its own food safety, but authorities there have liaised with the UK's Food Standards Agency in the past on EU food hygiene rules.
Jersey Dairy said it held the ISO 9001 international quality management standard and British Retail Consortium food safety standard. Independent auditors last inspected the firm in September this year.