The Food Safety Authority has confirmed it is investigating a salmonella outbreak.
There have been eight cases to date in Ireland.
It says it is working closely with the Department of Health and its counterparts in the UK, which has also seen a number of cases.
The investigation is trying to establish the source of the food poisoning, and laboratory tests are being carried out.
In the meantime, a company supplying implicated ingredients into the catering sector has withdrawn the products from sale.
The Food Safety Authority is advising food outlets providing ready-to-eat sandwiches to be particularly strict in adhering to best hygiene practices.
It reminds retailers of the importance of ensuring that hot sandwiches are thoroughly cooked before serving to the consumer.
It also reiterates the need for strict procedures to be followed at all times to avoid cross contamination between raw and cooked foods.
