A three-year-old boy playing with burners on a stove ignited the fast-moving fire that tore through a New York apartment building, killing 12 people, including four children, the city's fire department chief said Friday.

"We found that this fire started in a kitchen on the first floor. It started from a young boy, three and a half years old, playing with the burners on the stove," Fire Department Commissioner Daniel Nigro told reporters.

"The fire got started, the mother was not aware of it, she was alerted by the young man screaming," he said.

Mayor Bill de Blasio said Friday: "It seems like a horrible tragic accident."