Officials are trying to pinpoint why six passengers on a flight to Chicago from Germany fell ill.
Lufthansa spokesman Nils Haupt tells the Chicago Sun-Times that Flight 432 originating in Frankfort made an emergency stop Saturday night in London so an ailing passenger could be taken to a hospital there.
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Haupt says five more of the 309 passengers aboard the Boeing 747 then became sick after the flight continued on to Chicago's O'Hare International Airport.
One of those passengers was treated at the airport, and at least two others were taken to a Chicago hospital.
Haupt says the plane returned to Frankfurt early Sunday morning.