The Detroit Police Department's Eastern District building was evacuated after a person walked in holding a grenade.
The unnamed visitor entered the building Friday afternoon and announced, "Look what I found," Detroit Police spokeswoman Eren Stephens said.
The incident prompted the closing of Gratiot Street, where the police office is located, the Detroit News reported.
A bomb squad was called to the building and police public information officials said Department of Homeland Security personnel are assisting in the investigation.
No arrests were made.
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