Two teens on their way home from a London field trip were questioned Monday after officials discovered military-grade shells in their luggage.
TSA discovered two shells in their baggage at O'Hare International Airport Monday evening and contacted the FBI and Chicago Police.
The Transportation Security Administration says the bags belonged to a 16-year-old and a 17-year-old who were transferring to a flight to Seattle.
Officials evacuated the baggage room while the items were investigated. They were later cleared as inert.
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.
The teens weren't charged.
TSA is reminding passengers that large munitions are not allowed on board airplanes. Small arms ammunition can be packed in checked baggage.
For more information on the TSA's ammunition policies, please visit the TSA's official traveler information page.
The Associated Press Contributed to this story