A massive gas explosion leveled four buildings in Manhattan's East Village neighborhood on Thursday afternoon. Firefighters are still trying to fully extinguish the flames, and authorities are trying to figure out how many people may be missing or possibly dead. At least 25 people, including rescue personnel, were injured, some seriously.

Above you can see the moment the explosion occurred. The video was obtained by ABC New York from a local business security camera. Below you can see the immediate aftermath, with people trying desperately to make their way down a fire escape that seems to malfunction at first:

As you can see, at this point, just following the explosion, the buildings are still standing. Soon after, though, the force of the blast led to the collapse of four entire tenement buildings.

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At one point on Thursday, the smoke clouds were so large they could be seen and smelled from all over the city.

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It seems most likely that the incident was the result of a gas explosion. The building at 121 Second Avenue, where the initial blast occurred is quite an old building and, at least according to a Con Ed spokesman, had failed a recent inspection.