The development follows BBC's investigation last month in which iced drinks from popular high-street coffee chains Starbucks, Costa, and Caffe Nero were all found to be contaminated with varying levels of bacterial faeces.
Ice was tested for coliforms that are indicators of faecal contamination, which Defra - the government department that sets water standards in the United Kingdom - advises to be present not at all in water used for human consumption.
"It's extremely worrying", he said. He added, "When we're finding the sorts of numbers we're finding here, you have to look at the people making the ice, handling the ice, which they then transfer into the customers' drinks. And then you also have to look at hygiene failure with potentially the machines themselves: are they being kept clean?"
In a response, which was reported widely in the media, a KFC spokesman said: "We are shocked and extremely disappointed by these results".
British investigators tested 10 samples at each of the chains for traces of the microbes.
The management of all three fast food chains were quick to assure that hygiene is a top priority in their respective branches, but they also reinforced strict procedures after the shocking discovery.
A Burger King rep said the chain is working with its franchises in the U.K.to reinforce strict procedures set in place.
An expert labelled the findings "extremely worrying" as drinking water is unfit for human consumption if it contains any more than zero coliforms which puts into perspective just how unsafe these results are. "We immediately shut down the ice machines in the restaurants affected to conduct a thorough clean and inspection. we are awaiting the results of independent testing of the ice that will confirm they are back up to the standards we expect", a KFC spokesperson said.
There are safety standards in place for unfrozen drinking water, but none specifically for the production of ice.
Meanwhile Burger King assured that emphasis will be placed on training procedures for employees and McDonald's was open to work with relevant bodies to prevent ice contamination.