[Scan-DC] Metro Incident at Silver Spring station.

[Jeff Krauss]

This was a burning insulator under a train car, at an elevated 
portion of the track.
You could see the flames under the car at the trafficland.com 
Colesville & Wayne camera.
At one point the incident commander told the platform supervisor to 
switch to TG 7M.  That's an encrypted TG only available on a command 
officer's radio.  I presume there was some initial question about 
whether this was intentionally set, given the reports of an explosion.