Security screeners at Dulles International Airport discovered a live military-style smoke grenade in a traveler’s checked luggage.

The Transportation Security Administration said Thursday that a security alarm went off during a routine screening on Monday.

Upon closer inspection, TSA agents found a munition inside with a trigger device attached, along with the words “Smoke Yellow” on the side. A TSA explosives expert was called in, along with a state bomb squad to remove the device, which was determined to be a live bomb.

The TSA said the male passenger, whom they did not identify, told authorities that he bought the canister years ago at a military surplus store and thought it was inert.