"You have to look at the people making the ice, handling the ice, which they then transfer into customers' drinks. Low levels of two other indicator bacteria, coliforms and enterococci, were found in some ice samples. but, as they are widely distributed in the natural environment, they are not reliable indicators of potential health risks", McDonald's cited bacteriology and food safety professor Tom Humphrey.
Watchdog consulted with Tony Lewis, head of policy and education at the Chartered Institute of Environmental Health, on the findings.
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.
British investigators tested 10 samples at each of the chains for traces of the microbes.
It also suggests that workers at the chains are not keeping themselves clean and that they "have dirty bare hands", he said.
Among the results, four Burger King and five KFC branches revealed significant levels of contamination, which is saying a lot since there is no safe "minimum" level of contamination when it comes to the pathogenic bacteria, especially when it is for human consumption. "We have robust procedures in place with regard to the production, storage, and handling of ice in our United Kingdom restaurants", their spokesperson said.
A Burger King rep said the chain is working with its franchises in the U.K.to reinforce strict procedures set in place.
After finding out the results of the investigation, KFC immediately shut down the ice machines in question so it could begin its own inspection, and said it had "reinforced the importance of adhering to our strict procedures to all employees".
They added: "As the investigation highlights, there are no specific ice production standards in place, only those relating to unfrozen drinking water".
As one would hope, KFC, McDonald's and Burger King have all responded to this incident, claiming that hygiene is one of their top priorities at the fast food restaurants.
"[We] welcome the introduction of an agreed standard and would be happy to work with relevant industry bodies", a McDonald's spokesperson told Business Insider.