According to officials, the substance was discovered on the first floor of the building on High Street.
Emergency crews evacuated the first floor of the building.
Officials say three people have been exposed to the substance and are being examined at the scene before being transferred to a hospital.
HPD & HFD are investigating a suspicious substance at Fed Building at 135 High St. @CTDEEPNews assisting. No threat to any external area. Substance is isolated. Neighborhood is safe. Traffic in the area is shut down. pic.twitter.com/unPkg8JPRd
— D/C Foley (@LtFoley) February 8, 2018
There has been no word on any injuries at this time.
News 8 will update this story with more information as it becomes available.