(CNN) -- A package containing "explosive components" was left unattended for weeks in a Detroit federal building, resulting in the suspension of a building security guard, according to an official with knowledge of the case.
A joint terrorism task force is currently investigating the origins of the package, which was first discovered on February 26 at the Patrick V. McNamara Building.
It was then placed in a lost-and-found room before being reported to police last week, according to David Wright, president of the American Federation of Government Employees Local 918, which represents the Federal Protective Service workers.
"For some unknown reason, the ... private guard, picked up the package and decided to X-ray it, and when they saw something that looked out of place, that's when they contacted the FPS," Wright said. "He did not follow protocol."
The building houses offices of the FBI, the Internal Revenue Service and other federal agencies.
Wright called the mishap a "contracting mess," complaining that the use of private contractors impedes the security guard command structure.
"I cannot order one of these kinds of guards to do anything," he said.
The company in charge of the guards was not immediately available for comment.
"This is an ongoing investigation," said FBI Special Agent Sandra Berchtold. "The priority now is to determine what it was and who left it there."
The package was taken from the building, which was not evacuated, and detonated at Detroit's Belle Island, said police spokesman Samuel Balogun.
The package's contents were not immediately clear.
An FBI Terrorism Task Force is leading the investigation in collaboration with the Department of Homeland Security and Detroit Police.
No arrests were reported.