A bomb found inside a Detroit federal office building was not detonated by authorities until weeks after it was discovered, says a CNN report.

The package was discovered last Friday at the Patrick V. McNamara Building, which houses offices of the FBI, the Internal Revenue Service and other federal agencies, according to Department of Homeland Security spokesman Chris Ortman.

The package was taken from the McNamara building, which was not evacuated, and detonated at Detroit's Belle Island, the report says.

An employee with the Federal Protection Service, the security agency that guards federal property across the country, discovered the device on February 26, but reportedly stored the explosive in a locked room, the report says.

The incident is still under investigation.