The CIA left “explosive training material” under the hood of a Loudoun County school bus after a training exercise last week, a bus that was used to ferry elementary and high school students to and from school on Monday and Tuesday with the material still sitting in the engine compartment, according to the CIA and Loudoun County officials. As part of last week’s training exercise, CIA trainers placed explosive material into the engine compartment of a school bus on Thursday to test a dog’s ability to sniff it out. They also placed the material in parts of the school. Byard said the dog successfully found the material in the engine compartment, but some of the material fell deeper inside the compartment and became wedged beneath the hoses.