The Office of Hartford Mayor Luke Bronin says that there was a partial structure collapse in the morning hours at 213 Capen Street.
The Hartford Fire Department was called to the scene and evacuated everyone from the building without injury.
Police then closed Garden Street to north and southbound traffic between Edgewood Street and Greenfield Street, and Capen Street to east and westbound traffic between its intersections with Enfield Street and Garden Street.
The closure is expected to last through the day.
The City of Hartford Licenses and Inspections Division is currently assessing the building.
The incident remains under investigation.