The explosion appears to have started at 121 2nd Avenue and spread to 123 2nd Avenue, between 7th Street and St. Marks Place.
Here's what the buildings looked like before the fire:
Google Street View
121 2nd Avenue housed a Japanese restaurant called Sushi Palace. 123 2nd Avenue housed Pommes Frites, a french fry restaurant.
Via the FDNY's Twitter, it appears that 123 2nd Avenue has at least partially collapsed:
Now #FDNY operating on-scene at 123 2nd Avenue in Manhattan. pic.twitter.com/bg8vx1TwLX
- FDNY (@FDNY) March 26, 2015
The fire has definitely impacted both buildings, though:
Photo Manhattan 7th Alarm East Village. Credit Ann W Kim pic.twitter.com/EO9GUQPxRh
- NeEmergencyNewsWX (@NeEmergencyNews) March 26, 2015