UPDATE: The courthouse has been searched and staff has been allowed back into the building.

The Boston Federal Courthouse has been evacuated. There is no official word on the cause of the evacuation, but a reporter who was inside the building at the time of the evacuation says, "We were inside and all of a sudden we heard, 'Code Red, everyone out,' and I was just told by a law enforcement source that someone had called in a bomb threat."

We will bring you more details as they become available.