On February 26, 2011, a security guard at a Detroit office building that houses, among others, an FBI field office found a suspicious canvas bag with a small safe inside nearby . After examining it multiple times, the guard stashed it under a desk in a security office.

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It wasn't until three weeks later that they discovered that there was a bomb inside. A year later, a federal review laid blame on the incident on that guard, his employer and other agencies share blame for the oversight, CNN reports.

CNN says that the bag, which stayed under a desk for 21 days, was not considered suspicious because the place where the bag was being held is used to store personal property.

The security guard who originally found the device was subsequently fired, CNN says.

READ MORE at CNN.com.