This Monday photo provided by the Transportation Security Administration (TSA) shows two World War I artillery shells discovered by baggage screeners in checked luggage that arrived on a flight from London at Chicago's O'Hare International Airport. The TSA said the bags belonged to a 16-year-old and a 17-year-old who were returning from a school field trip to Europe. The teens told law enforcement they obtained the shells at a French World War I artillery range. It was not clear how. TSA explosives experts believe they are French 75 mm shells. A bomb disposal crew determined the shells were inert and no one was ever in danger. The teens were questioned then allowed to travel onward. They weren't charged.