Several of its police officers were treated for a possible exposure to fentanyl and heroin, according to the Hartford Police Department.
The incident took place around noon Thursday when officers were attempting to serve a search warrant in relation to an active investigation, the department said on Facebook.
One of the suspects of the investigation threw a package possibly containing heroin or fentanyl, at a window, sending the powder into the air inside the apartment, they said.
Several officers were exposed to the substance and were decontaminated on scene by Hartford Fire Personnel.
The substance is being tested to confirm that it is indeed fentanyl or heroin, or both.
HPD officers assisted residents of the building in evacuating the area.
Garden Street, between Mather Street and Albany Avenue, is closed due to further investigation and decontamination.
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