Restaurants, bars and takeaways in Nottingham are being issued with an unusual request by hygiene experts.
The city council's food safety teams are carrying out random checks to try to limit food poisoning.
They are focusing their efforts on bacteria which can linger in ice buckets and the machines which make the cubes, rather than food preparation.
In 2004, 300 incidents of food poisoning in Nottingham were reported to officials.
Paul Dales, Nottingham City Council said: "We have found some levels of bacteria which have given us some concern.
"We have returned to those businesses to ensure that they clean the machines and they are given advice on how to handle and store the ice correctly.
"Should they fail to take the advice we would have to serve improvement notices and possibly take formal action like prosecution."