New York fire: What we know so far about Bronx apartment block blaze

At least 12 people have died and several more critically injured in fire at an apartment block in the Bronx in New York City.

Four children were among the dead, in "the worst fire tragedy in at least a quarter of a century", the city's mayor Bill de Blasio wrote on Twitter.

“It is unspeakable, and families have been torn apart,” he added.

Here's what we know about the fire so far:

What caused the fire?

Officials said the first alarm sounded at the five-storey building at around 7pm local time (00:00 GMT). Firefighters extinguished it before 10pm ET.

Authorities said the fire began on the first floor of the building on Prospect Avenue in the Belmont area of the Bronx.

They added that it spread quickly, as wind fanned oxygen to the flames.

But the cause of the blaze is still unknown and it could take months for investigators to work out what started it.

New York City Fire Commissioner Daniel Nigro described the tragedy as “historic in its magnitude”.

The building is believed to be more than 100 years old and contained around 20 apartments, according to the The New York Times.

Who were the victims?

None of the 12 victims have yet been named and four people are reportedly to be in critical condition in hospital.

It is known that those who died on various floors of the building.

Four children aged one, two and seven and another boy died in the fire, along with four men and four women. One of the victims is known to be over 50.

Authorities said firefighters managed to rescue 12 people from the burning building.

Those who managed to escape were subjected to bitterly cold conditions as temperatures dropped as low as -10C.

One woman who witnessed the fire told the BBC: “People were screaming Fire! Help! Fire Help! We knew there was trouble.”