On Decemeber 22 there was a sizable explosion in Ballston near the Hilton hotel. Police had Stuart and Stafford streets closed when I drove past around 5pm.
It turns out the electrical transformer, a large green box that steps down high voltage current before it goes into a building, faulted and exploded. Not sure if there where any injuries, but a witness did say they saw rescue workers with stretchers present.
Here is a picture of the new transformer being installed after the damaged one was removed.