At least 13 people were injured during a rush-hour shooting at a subway station in the New York borough of Brooklyn Tuesday, where authorities said “several undetonated devices” were recovered amid chaotic scenes.

Ambulances lined the street outside the 36th Street subway station, where a New York police spokeswoman told AFP officers responded to a 911 call of a person shot at 8:27 am (1227 GMT).

Unverified video footage posted on Instagram appeared to show passengers tending to bloodied victims lying on a smoke-filled station platform.

The images showed subway staff shepherding panicked passengers, some still clutching their morning coffee cups, off the platform and into the carriages of a stationary train. A sign saying 36th Street can be seen in the background.

An unidentified person can be heard saying that a fire had been set in the train car, and that he saw “at least eight people” shot.

According to NBC, citing NYPD and senior law enforcement officials, a man in a gas mask and orange construction vest may have tossed a smoke canister on the platform to distract the rush hour crowd.

The suspect was still at large, according to Manhattan borough president Mark Levine.

The city's fire department gave a toll of “13 injuries at this time,” while ABC News quoted police sources as saying at least five people were shot in the incident.

The police department tweeted that there were “NO active explosive devices at this time.” “Please stay clear of the area” the NYPD tweeted, urging witnesses to contact a police tip line with any information.

The White House said President Joe Biden had been briefed on the incident and was in communication with New York officials.

New York governor Kathy Hochul tweeted that first responders were on the scene and promised regular updates as the investigation unfolds.

Mass casualty shootings happen with relative frequency in the United States, where firearms are involved in approximately 40,000 deaths a year, including suicides, according to the Gun Violence Archive website.

Shootings in New York City have risen this year, and the uptick in violent gun crime has been a central focus for Mayor Eric Adams since he took office in January. Through April 3, shooting incidents rose to 296 from 260 during the same period last year, according to police statistics.

The incident came just a day after US President Joe Biden announced new gun control measures, increasing restrictions on so-called “ghost guns”, the difficult-to-trace weapons that can be assembled at home.

Lax gun laws and a constitutionally guaranteed right to bear arms have repeatedly stymied attempts to clamp down on the number of weapons in circulation, despite greater controls being favored by the majority of Americans.

Three-quarters of all homicides in the United States are committed with guns, and the number of pistols, revolvers and other firearms sold continues to rise.