Tod Seelie/Gothamist

The hottest party in New York City last weekend may not have been at any of the city's various clubs or night spots, but buried beneath them.

Photos from an underground party held in an abandoned subway station surfaced on the New York news website Gothamist this week showing dozens of individuals watching dancers and listening to live music in an abandoned subway station.

Now, the Metropolitan Transportation Authority and the New York Police Department are investigating the photos.

"Trespassing in non-public areas … is a serious crime and has the potential to lead to injury," the MTA said in a statement to ABC News. "This incident has been passed on to the NYPD for investigation."

The NYPD did not respond to request for comment.

The outing, organized by a secret-events promoter named Jeff Stark, who runs the company Nonsense NYC, was half-party and half-performance.

Writer John Del Signore attended the party for Gothamist and described meeting up with the event organizers and a crowd of nearly 200 people at an undisclosed location, and then watching as the partygoers dropped through a hatch into the subway station at the directions of the party's secretive "agents."

About twenty people remained, and then I understood that they were dropping down into a hole in the sidewalk. The Agents stood quietly around a hatch, urging participants to quickly scramble down a ladder into the darkness. To be clear, this was not a desolate area, and as I reached the hatch, a man and a woman approached from the opposite direction, holding hands and gazing with disbelief as the last of us were willingly swallowed up by the city. I tried to smile normally at them as I went down the ladder, followed by the rest of the Echo Vault staff. The hatch creaked shut behind us, and there was silence, aside from the chatter of the Agents communicating over their lapel mics.

Tod Seelie/Gothamist

Del Signore described performers chanting and playing instruments on a "stage" in the vaulted underground space. At the end of the night, they scrambled back up the dark concrete steps and into the city, where they were instructed to go "far, far away" as fast as possible, he wrote.

Stark's company bills itself as host of "weird events" on its website:

"Nonsense NYC is a discriminating resource for independent art, weird events, strange happenings, unique parties, and senseless culture in New York City."

Stark did not immediately respond to requests for comment.