The stomach ailment that grounded a group of Scandinavian tourists likely was not a Chicago souvenir, officials said Tuesday.
Seven members of a tour group fell ill Monday night before boarding a Scandinavian Airlines aircraft at O'Hare International Airport and were taken to nearby hospitals around 11 p.m.
Later, two other travelers took sick after boarding Flight 944, which led the pilot to require all members of the group to leave the airplane before it departed for Copenhagen, Chicago Fire Department spokesman Larry Langford said.
"The pilot made the decision not to have anyone on the tour on his aircraft as he didn't want anyone becoming violently ill over the ocean," Langford said.
The Norwegian tourists numbered about 52 people, authorities said, and were on a bus trip from Memphis. Tenn., to Chicago.
Chicago Department of Public Health investigators are checking with food vendors and others with whom the group came into contact. It's thought the bug was contracted outside of Chicago, spokesman Brian Richardson said.
The preliminary diagnosis is the norovirus, a contagious virus that can cause vomiting and diarrhea. It's spread through contaminated food or from contact with infected people and surfaces.
The rapid succumbing of the tourists would fit the profile of norovirus, but the department cannot confirm that diagnosis, Richardson noted.
"With norovirus, there's a quick turnaround time," he said. "We recommend that anyone who's traveling, remember to wash your hands to help prevent the spread of viruses."
Chicago Fire Department sent multiple ambulances to the International Terminal and patients were taken to Advocate Lutheran General Hospital in Park Ridge and Resurrection Medical Center in Chicago.