Fatal New York fire lit by child playing with stove.

Fire commissioner said today that a preschooler toying with the burners on his mother’s stove accidentally sparked New York City’s deadliest fire in decades, an inferno that quickly overtook an apartment building and blocked the main escape route.

Excluding 9-11, it was the deadliest blaze in the city since 87 people were killed at a social club in the same Bronx neighbourhood in 1990. A fire in a home in another part of the Bronx killed 10 people, including nine children, in 2007.

A dozen people died, and four others were fighting for their lives a day after the flames broke out in the century-old building near the Bronx Zoo.

Officials said that the 3 1/2-year-old-boy, his mother and another child were able to flee their first-floor apartment. But they left the door open behind them, and it acted like a chimney that drew smoke and flames into a stairwell. From there, the fire spread throughout the five-story building.

At least 20 people scrambled out via fire escapes on a bitterly cold night, but others could not.

Fire Commissioner Daniel Nigro said, “People had very little time to react.Firefighters arrived in just over three minutes and saved some people, but “this loss is unprecedented.”

One family lost four members: Karen Stewart-Francis, her daughters, 2-year-old Kiley Francis and 7-year-old Kelly Francis, and their cousin, 19-year-old Shawntay Young, relatives said. Stewart-Francis’ husband, Holt Francis, was hospitalized, the family said.

The building had roughly 20 apartments, which were home to people from the U.S. and immigrants from the Dominican Republic and Guinea.

About 170 firefighters worked in 15-degree weather to rescue dozens of people.

Residents described opening their front doors to see smoke too thick to walk through and descending icy fire escapes with children in hand. Some escaped barefoot or in their nightclothes.

The boy who accidentally started the fire had played with stove burners before, Nigro said