A noise that sounded like an explosion just occurred in Manhattan's Chelsea neighborhood around 8:30 p.m., on West 23rd Street, between 6th and 7th Avenues. Mayor Bill de Blasio said there was no known connection to terror, but said that so far, it appears it was "an intentional act."

UPDATE 11:20 p.m.: During a press conference, the Mayor said there were a "significant" number of injuries—29, including one that could be called serious. He stressed that based on the preliminary investigation, it did not seem that the blast was related to terrorism, adding, "There is no specific and credible threat against NYC."

He praised the NYPD and all other agencies for being well-equipped to handle the situation, "Whatever the cause, whatever the intention, New Yorkers will not be intimidated." Also, it didn't appear, de Blasio said, that there was a link to the Jersey Shore pipe bomb incident.

The mayor also asked that anyone with tips, photos and video to contact the NYPD at 800-577-TIPS.

NYPD Commissioner James O'Neill said the explosion occurred outside 131 West 23rd Street. Police officers patrolling west on West 23rd between 6th and 7th Avenues actually saw the blast and called for additional units. They've ruled out gas as a cause of the blast, "The exact nature has not yet been determined." The FDNY is investigating any structural damage to buildings in the area.

It was confirmed that West 27th Street between 6th and 7th Avenues was being investigated.

FDNY Commissioner Daniel Nigro said of the 29 injuries, 24 people were taken to hospitals, "None of these are life-threatening." Also, other FDNY units in the area heard the blast and responded.

However, officials did not give any other details about the investigation. They didn't confirm that the dumpster was involved in the blast. O'Neill did say there was video of the explosion they have seen.

Here's the press conference:

This video shows the explosion from across the street:

Leaked video of the initial explosion in #Chelsea pic.twitter.com/nBMbh7iBCl — REGATED (@regated) September 18, 2016

UPDATE 12:20 a.m.: The NYPD just issued a "precautionary measure" to those living on West 27th Street between 6th and 7th Avenues:

Please be advised of this update regarding the incident in Chelsea, NYC pic.twitter.com/Ux5dfBsj72 — NYPD NEWS (@NYPDnews) September 18, 2016

UPDATE 10:55 p.m.: At least 25 people suffered injuries (which do not appear to be life-threatening). The 1 and 2 trains are not running between Chambers and 34th Streets, while the E and F have changes and delays—basically don't expect train service near 23rd Street as police investigate.

CNN is reporting that gas has been ruled out as a cause and that a construction toolbox at a nearby buildng site was being inspected. Further, NYPD Special Operations Tweeted:

A possible secondary device has been located @ 27th Street, 6th - 7th Avenues. #NYPD nvestigations are ongoing. Avoid the area @NYPD13Pct — NYPD Special Ops (@NYPDSpecialops) September 18, 2016

Officials will be speaking at a press conference shortly.

EARLIER:

Very serious scene at 23rd and 6th Ave in NYC after incredibly loud noise (explosion?) shortly after 8:30 pic.twitter.com/oRv6uU05LM — Alexandra Sowa, M.D. (@AlexandraSowaMD) September 18, 2016

The FDNY says 25 people were injured, "None appear to be life-threatening at this time." A facility for the blind, VISIONS at Selis Manor, is located at 135 West 23rd Street; its website calls itself "an adapted learning environment and meeting place for blind youth, adults and seniors."

A reader who was walking from the High Line could feel and hear the blast at West 19th Street and 7th Avenue. He described the sound as "like fireworks in terms of bass and volume, but only one large boom and definitely low to the ground."

Another reader who lives five blocks away on West 28th Street said he and his wife felt their apartment windows rattle.

Businesses appear to be (self?) evacuating:

The FDNY could not confirm what caused the noise/possible explosion.

WABC 7 reporter CeFaan Kim says a child in a car was injured by an apparent blast:

Explosion on 23rd and 6th. These two cars had back windows blown out while driving. 8 year old in back seat injured. pic.twitter.com/aKDra2LaIC — CeFaan Kim (@CeFaanKim) September 18, 2016

There is, of course, a large response in the area:

@NYPDNews Due to explosion at 23rd St btw 6th & 7th Ave, MN, expect train service delays/cancellations, street closures, & traffic delays — NYCEM - Notify NYC (@NotifyNYC) September 18, 2016 Police are ordering pedestrians to move from 23rd to 22nd street pic.twitter.com/V12ReH70gY — Corey Johnson (@CoreyinNYC) September 18, 2016 Bomb squad just arrived... Block has been cordoned off between 6th and 7th on 23rd st. pic.twitter.com/vnZ4TxciGj — Valdio Toar (@V_ToaR) September 18, 2016

It's unclear where the blast may have originated from; this photograph of a dumpster that was apparently damaged is circulating:

Earlier today, a pipe bomb exploded in a plastic trash can in Seaside Heights, NJ; other devices that failed to detonate were also found.

We'll update as we learn more. You can send tips to tips@gothamist or Tweet at @Gothamist.