Multiple people shot at in subway station in New York's Brooklyn

Several people were shot at in a subway station in New York's Brooklyn today. People tweeted photos showing commuters with blood on their clothes being helped by others, as they sat with their back to a metro train. At least 16 were injured.

The shooter was suspected to be still active in the area at the time this report was published.

Some reports said explosive were found at the site of the attack, which happened during the morning rush hour at 8:30 am local time. Trains have been stopped, local media reported.

The New York Police Department, or NYPD, tweeted, "Due to an investigation, avoid the area of 36th Street and 4th Avenue area in Brooklyn. Expect emergency vehicles and delays in the surrounding area."

The NYPD said there are "no active explosive devices".

The authorities are yet to confirm if this was a terror attack.

Some photos on social media show blood on the floor of a metro coach in the Brooklyn subway. Several Twitter users have indicated this could be a terror attack.

NY1 News reported the suspect wore a construction worker uniform and a gas mask.

According to NBC, citing NYPD officials 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.

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

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 favoured by the majority of Americans.