A small child playing with a stove is thought to be the cause of a massive five-alarm fire in the Bronx on Thursday that killed at least 12 people, New York Mayor Bill de Blasio said.

• New York City fire kills 12, sends residents scrambling
• The dead include family of 4, several young children
• Investigators: Fire started on 1st floor, spread up a stairwell

The 3 1/2-year-old boy was playing with burners on a stove at about 7 p.m. before flames erupted, engulfing an apartment building and blocking the main escape route.

The boy, his mom and another child fled their first-floor apartment on the 2300 block of Prospect Avenue in Belmont, but the fire was drawn into a stairwell, where the flames traveled up like a chimney, the Associated Press reported.

Among the dead were a family of four: 2-year-old Kylie Francis, 7-year-old Charmela Francis, 19-year-old Shantay Young and 37-year-old Karen Francis.

Investigators also identified 58-year-old Maria Batiz, 7-month-old Amora Vidal, 28-year-old Emmanuel Mensah, 49-year-old Donkor Sollomon and Justice Opoku.

Two other victims, a 12-year-old boy and a 50-year-old man, have not yet been identified.

Several people were hospitalized in critical condition.

“People had very little time to react,” Fire Commissioner Daniel Nigro told the AP. Firefighters who arrived in just over three minutes “bravely entered the building and did everything they could — we did save a number of residents — this loss is unprecedented.”

De Blasio and Nigro called the tragedy historic while speaking at the scene Thursday.

"Tonight here in the Bronx, there are families that have been torn apart. This is the worst fire tragedy we have seen in this city in at least a quarter century," De Blasio said.

"In a department that's certainly no stranger to tragedy, we're shocked by this loss," Nigro added.

Almost 200 firefighters battled the blaze at the walk-up building near the Bronx Zoo. Temperatures in the teens with wind chills in the single digits added to the difficulty of their battle.

Thursday's deadly fire is reminiscent of a similarly devastating one from 2007. That fire took the lives of 10 Malians living in the Highbridge neighborhood of the Bronx. Nine of the victims were children, and five of those kids were from the same parents.

Tougher fire codes for buildings were implemented at the turn of the 20th Century after a string of catastrophic fires. But the Bronx building where 12 died Thursday was not new enough that it was required to have modern-day fireproofing, such as sprinkler systems and interior steel construction.

The management company for the building’s owner, D&E Equities, declined to comment Friday, but the building doesn’t have a major history of housing violations, a city official told the AP.

Information from the Associated Press was used in this report.