The Illinois Department of Public Health announced the illnesses Friday. Throughout the weekend, Six Flags Hurricane Harbor has remained closed, the Chicago Tribune reported.
"The water park is closed," Melanie Arnold, spokeswoman for the department, said Saturday. "The Illinois Department of Public Health is having (Six Flags Hurricane Harbor's) water hyper-chlorinated for eight hours, and then there will be more sampling and analyzing."
Arnold told the Tribune the water could have contained the culprit for an infection called cryptosporidium, which causes diarrhea, fever and vomiting. Cryptosporidium is "one of the most common causes of waterborne disease within humans in the United States," the Centers for Disease Control and Prevention said.
Jim Taylor, park spokesman, said there is no link between the water park and the illnesses.