An explosion rocked the East Village on Thursday afternoon, leading to four buildings on Second Avenue between East 7th and 8th streets to catch fire, and causing two to collapse.  

A preliminary investigation indicated gas or plumbing problems caused the explosion at 121 Second Ave., which was reported at 3:17 p.m. Mayor Bill de Blasio said in a press conference about two and a half hours after the fire that a stop work order was issued for the building after it didn’t pass an inspection earlier in the day. Con Edison was on site an hour before the explosion. 

There were no reported fatalities or missing persons as of Thursday evening, and 12 people -- three in critical condition -- were being treated for their injuries. FDNY Commissioner Daniel Nigro said two of the three people listed in critical condition had burns to their airwaves, and one person fell unconscious after the explosion.

Before there were answers, the streets flooded with bystanders who watched some 250 firefighters arrive to battle the 7-alarm blaze. People shot photos and video with their cell phones, congregated and speculated the cause as police officers pushed the crowds further away from the site. 

“I was in my apartment and I heard some guy screaming that a building exploded,” said Violet Moore, who lives in a building on Second Avenue about three blocks away from the site.  

“I saw 9/11 and this is jarring,” said Miche Griffin, who lives in the same building as Moore. Griffin said she hoped the cause of the explosion and subsequent fire wasn’t intentional, and due to an accident such as a gas leak. 

A woman who worked nearby said the explosion sounded more like a thump than a boom, which she initially blamed on children playing upstairs. When she walked out to get a slice of pizza on Second Avenue and 5th Street, she learned what caused the boom she heard earlier. 

"Our thoughts and prayers are with everyone of them and their families," said de Blasio. "We are praying no other individuals are found injured and there are no fatalities."

There were no confirmed complaints about a gas leak before the explosion, but de Blasio warned all New Yorkers to still report any suspicious smells to 311 and Con Edison. 

“We will be here for a very long night,” said Fire Commissioner Daniel Nigro. Firefighters spent the first 15 minutes on scene doing “extremely dangerous searches of these buildings,” Nigro said, before being forced out by the collapses of 121 and 123 Second Ave.