New York City Mayor Bill De Blasio said investigators believe the Bronx fire which killed 12 people was caused by a child playing with a stove.

The four-alarm fire – five being the highest level of alert – began on Thursday evening in a neighbourhood near the Bronx Zoo and by the next morning had turned into the city’s deadliest blaze in nearly 25 years.

Mr De Blasio called it “an unspeakable tragedy in the middle of the holiday season” during a news conference at the scene, amid subfreezing temperatures in the city. His spokesperson Eric Phillips also announced the suspected cause of the fire on Twitter.

Among the victims was a one-year-old child found in a bathtub being cradled by its mother. Both perished. A two-year-old and seven-year-old were also among the 12 victims. Four people remain in critical condition.

At least 14 people were injured, including seven emergency response staff. The Washington Post said officials believed the fire was started by a three-year-old playing with rings on a stove. The fate of that child was not immediately known.

Firefighters responded within a few minutes of the initial emergency call at 7pm local time, with 170 of them on the scene within three hours working to put out the blaze and rescue any residents trapped in the five-storey building with 25 apartments.

'People were screaming': Bronx fire eyewitnesses relive what they saw

New York City Fire Department commissioner Daniel ­Nigro said the fire began on the first floor, and residents said they were surprised at how quickly the flames spread in the nearly century-old residence.

One man, Jamal Flicker, told the New York Post: “The smoke was crazy, people screaming, ‘Get out!’ I heard a woman yelling, ‘We’re trapped! Help’.”

Due to where the fire started, investigators said it blocked the main stairwell in the building, one of the major escape routes.

New York City apartment fire Show all 11 1 /11 New York City apartment fire New York City apartment fire People comfort each other after the New York apartment fire Reuters New York City apartment fire The building where the major house fire happened Getty Images New York City apartment fire At least 12 people have been killed and four more critically injured from the fire EPA New York City apartment fire People stood around in the streets after being evacuated from the building Getty Images New York City apartment fire Over 170 firefighters responded to the evening fire Reuters New York City apartment fire The blaze broke out in building on Prospect Avenue Reuters New York City apartment fire A close up view of one of the flats in the apartment building Getty Images New York City apartment fire The victims include a one-year-old child REUTERS New York City apartment fire Mayor Bill de Blasio said at a press conference from the scene that 'it is the worst fire tragedy we have seen in this city in at least a quarter century.' REUTERS New York City apartment fire People outside the building after the fire Reuters New York City apartment fire Firefighters look on to the damaged building Getty Images

Mr Nigro said “people died on various floors of the apartment” and confirmed the investigation will continue.

Though the building was not new enough to require state-of-the-art fire and smoke detection or a sprinkler system, it was still subject to minimum building codes of the city.

According to records from the New York City Department of Housing Preservation and Development, the building had at least one open violation “involving a defective carbon monoxide detector, and a faulty smoke detector in a unit on its first floor,” according to the New York Post.

The violation had been reported back in August 2017.

However, it remains unknown at this time what, if any, actions were taken by building owners – listed as D&A Equities – to remedy the problem.

“The building owner, building management is supposed to make sure that all those basic safety precautions are in place, and this is an older building,” Mr De Blasio told CNN, adding that fire investigators will need more time to look into the incident.