NYU students were evacuated Thursday afternoon from Green House at Seventh Street Residence Hall and the Tisch Dance Company on Second Avenue following a massive explosion and seven-alarm fire on Second Avenue between Seventh Street and St. Marks Place.

The fire was reportedly caused by a gas-related explosion in the restaurant Sushi Park at approximately 3:17 p.m. 123 Second Avenue, the building next door that houses the restaurant Pommes Frites, collapsed after the fire spread to an additional three buildings. The New York City Police Department reported the fire was contained to four buildings, and Con Edison has shut down gas service in the area.

The fire injured at least 19, with three in critical condition. Those three people in critical condition were brought to the Bellevue Hospital Center officials said.

Debris from the explosion littered Second Avenue and smoke could be seen for blocks in every direction. The New York Police Department evacuated the area and closed off 2nd Avenue from East Fourth Street to East 12th Street.

Michael Cummings, a 39-year-old who works at The Sock Man on St. Marks Place, said he heard the explosion and ran to the scene where he saw a lot of debris falling and flames rising from the building.

“I ran where everyone else was running, around the corner, to Second Avenue, and what I saw was a building that had the front of it blown off,” Cummings said. “There was a woman on the fire escape, trying to get off, and she was having trouble getting down, and people were trying to climb up to help her.”

Mayor Bill de Blasio spoke to the media at 5:30 p.m. on the status of the buildings and the cause of the explosion.

“Preliminary evidence suggests a gas-related explosion,” de Blasio said. “That investigation is ongoing. The initial impact appears to have been caused by plumbing and gas work that was occurring inside 121 Second Avenue.”

De Blasio also said Con Ed officials had visited the work being done on the building earlier in the day, but the building did not pass inspection.

“The preliminary report, because we’re still waiting to get the full download from the Con Ed crew, is that they observed the work, it did not pass inspection, they gave further instruction,” de Blasio said. “That was earlier this afternoon, but again, we are not going to speculate on details until we have a full report.”

NYU junior Ian Reagan said he was napping in his room at 13 St. Marks Place when the sound of the explosion woke him.

“I was napping in my room and heard a big explosion — there were some screams,” Reagan said. “It kinda sounded like a bomb but I’ve never heard a bomb before.”

Volunteer with the Coalition for the Homeless Cassandra Edwards, 40, was at the halfway house across the street at the time of the explosion. Edwards said she heard a loud noise, and police eventually came in and ordered the building to be evacuated.

“It sounded like a big boom,” Edwards said. “We were across the street from the explosion, and when it happened it rocked all the buildings in the area. We came around here because they were afraid the building was going to collapse because it was engulfed in flames. We were just in shock, like I can’t believe this, that right across the street this is happening.”

The NYPD announced that a displacement shelter has been setup at PS 63 at 121 E. Third St. The university announced that students evacuated from Green House will be housed in Palladium. Additionally, the New York City Department of Health has recommended that those in the vicinity of the fire stay inside when possible and keep all windows closed until the smoke clears.

Additional reporting by Felipe de la Hoz.

Email Alex Bazeley at [email protected].