Baggage screeners at O’Hare International Airport have discovered two World War I artillery shells in checked luggage that arrived on a flight from London.

The Transportation Security Administration says the bags belonged to a 16-year-old and a 17-year-old who were returning from a school field trip to Europe.

TSA spokesman Jim McKinney says a bomb disposal crew determined the shells were inert and no one was ever in danger.

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 77 mm shells.

They were seized Monday evening while the teens were transferring to a flight to Seattle.

The teens were questioned then allowed to travel onward. They weren’t charged.