It started around 5:15 a.m. Tuesday at the Lenox house, a historic building on the Seminary's property. It reached two alarms.
The building is located in the rear of the Seminary's property on the unit block of Library Place which is close to the Princeton University campus.
The building is near the Seminary's library.
Chopper 6 over the scene showed flames shooting from the roof.
No injuries have been reported at this time.
The fire shut down Route 206 around the Seminary.
There is no word on a cause.
Princeton Theological Seminary was established in 1812, the first Seminary founded by the General Assembly of the Presbyterian Church.
The Lenox House contains faculty offices and seminar rooms for classroom use.
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This article has been updated to show the fire broke out at the Lenox House on the Seminary's property, but not at the library itself.