Update 1:55 p.m.
The Detroit News reports that three police officers have been temporarily quarantined, including the officer who handled the letter and two who were in the immediate vicinity.
The News quotes Inspector Don Johnson of the Homeland Security Unit of the Detroit Police Department:
"The officer who was exposed doesn't appear to be in any pain or distress at this time. At this point, we are treating it more as a hazmat situation rather than a bomb situation."
The FBI and Department of Homeland Security are responding to a situation at a Detroit Police Station.
The police station at the corner of Schaefer and Grand River was evacuated and a Hazmat team dispatched after a suspicious powder fell out of a mailed envelope. The envelope had no return address.
Hazmat crews are still analyzing the substance.