Fast food chain KFC launched an investigation after a BBC researcher was served ice with bacteria from faeces on it.
The discovery was made at the KFC branch in Birmingham's Martineau Place by researchers from BBC One's Rip Off Britain show.
They were looking into food hygiene standards at several big name takeaways and coffee shops. Most of the samples turned up low and harmless levels of bacteria, they said.
Dr Margarita Gomez Escalada, who examined the results at Leeds Beckett University, told the programme: "We found high levels of bacteria in the ice. 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."
In a statement KFC told the programme that it was "extremely disappointed" by the ice test results adding that it had "immediately launched an investigation".
KFC also said they were undertaking "a retraining programme with all team members on our standards for touch point cleaning and procedures". The restaurant chain added that it takes "food safety and hygiene extremely seriously".