It's the cold truth: Some fast-food and casual dining restaurants in Chicago are using bacteria-filled ice cubes to cool down customers' drinks.

A test of ice cubes by the Chicago Sun-Times from 49 eateries and bars found that one out of every five samples contained high levels of bacteria.

Samples from three of the restaurants tested had an undetermined amount of fecal coliform, according to the report.

Bacteria, including fecal coliform, aren't dangerous for most people but can lead to illness, experts say.

"It's not like you'll see people dropping over dead or huge numbers getting sick because it's going to take just the right bacteria and the right person to make them ill," said Brian Swistock, co-author of Penn State University's publication "Water Tests: What Do the Numbers Mean?"

To compare, a water sample taken from a toilet in a men's room at the Sun-Times tested cleaner that ice cubes from 21 of the restaurants and bars tested.