UPDATE: The T announced the resumption of service at 4:50 p.m.
An inbound D train derailed between Hynes and Copley Square. Brian Campbell reports a friend called to say she's now covered in soot after something began burning and passengers had to walk through the tunnel to Copley:
She was on an inbound train and evacuated in the tunnel between Hynes and Copley, they exited at Copley.
The T is now running buses instead of trolleys between Park Street and Kenmore Square.