For anyone who was alarmed by the swath of yellow "police line" tape that wrapped the northeast corner of Sterling and Franklin this afternoon (it was later reduced to a small segment of the street, shown above), you can rest assured no crime was committed. Rather, Con Ed was dealing with a manhole fire, a surprisingly dangerous and potentially destructive occurrence that is relatively commonplace in New York City. Often the product of drainage issues after snow and ice storms, the blazes are caused by the decay of wiring and wire casings, which can catch fire. The real danger is that the fires release gases which themselves can ignite in the presence of the electricity (the first link above describes the phenomenon as similar to a bolt of lightening), causing explosions that can launch manhole covers and flames fifty feet in the air, scaring the beejeezus out of residents and occasionally proving fatal.
In the case at Franklin, the Con Ed folks got there quickly enough to begin diffusing the situation, so explosions were unlikely (their red truck is in the background of the first photo). Still, if you ever see a whole lot of smoke and steam that doesn't just smell like steam pouring out of a manhole, don't stand to close to it.