KFC has promised a full investigation after bacteria from poo were found on the ice it serves in drinks.
Undercover investigators for the BBC's Rip Off Britain programme say they found 'high levels' of the faecal bugs when investigating hygiene standards at fast food restaurants.
Swabs were taken from ice at the chain's Martineau Place, Birmingham, branch, and sent off to a lab at at Leeds Beckett University for analysis.
"We found high levels of bacteria in the ice," Dr Margarita Gomez Escalada told the programme.
"The presence of faecal coliform suggests that there's faecal contamination either on the water that made the ice, or the ice itself, and so it increases the risk of getting sick from consuming this ice."
Faecal coliform is found in the faeces of humans and other animals, and isn't harmful in itself. However, finding it in the ice sample implies that the ice has come into contact with poo - leading to the risk of several nasty diseases.
Recently, for example, customers at a Nottingham restaurant fell ill with food poisoning thanks to an E. coli infection that was caused by food contaminated with faeces.
The KFC branch investigated by the BBC had only weeks before been given a five-out-of-five rating by the Food Standards Agency following a big clean-up - it had previously been awarded a zero.
In a statement, KFC told the programme that it was extremely disappointed and that it has launched an investigation - as well as 'a retraining programme with all team members on our standards for touch point cleaning and procedures'.
Samples taken at Costa in Loughborough, the Chicken Cottage in Hampstead, a Café Nero in Bath and the Wimpy in Basildon all revealed harmless levels of bacteria.
But even the smartest of restaurants can suffer from poor hygiene. Two years ago, for example, Marco Pierre White's Steakhouse in the Cube in Birmingham was given a zero rating from the Food Standards Agency.
A few months later, the same thing happened to London's exclusive Hospital Club, set up by Eurythmics star Dave Stewart and Microsoft co-founder Paul Allen - thanks to mouse poo rather than human in this case.
If you're concerned about the hygiene rating of a restaurant, you can check it on the Food Standards Agency website, here.