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 it looked like down at the scene:
The area around the fire was shut down for several surrounding blocks.
This building was completely engulfed in flames.
More than 200 firemen responded to the scene.
News crews and bypassers stopped on St. Marks Street and 3rd Avenue to catch a glimpse.
People who lived nearby waited by the police barricades in order to return home. They had to tell the officers where they lived before being admitted, as a safety precaution.
Tarun Kundu owns the printing shop, Kings Copies, on the ground-level of one of the burning buildings.