Mayor de Blasio said the city is investigating whether there was a delay in getting EMTs to a fire where two 4-year-old children died Sunday after one of them may have been playing with a lighter.
The blaze began in the basement of the home on Bay 30th Street just before midnight.
Within minutes of police and firefighters arriving, the children, Jai'Launi Tinglin and Ayini Tinglin, were carried outside and rescue workers tried to resuscitate them as neighbors watched.
Officials said the children, half-siblings, died of smoke inhalation.
The FDNY said the first 911 call was received at 11:51 p.m. As per policy, an ambulance wasn't assigned until fire was confirmed. That was at 12:05 a.m., according to published reports.
The ambulance arrived at 12:12 a.m., seven minutes later.
A neighbor, Ronda Clarke, told the New York Times that firefighters could be heard wondering aloud when the EMTs would arrive.
"They were very upset," Clarke said. "They were saying, 'Where is EMS?'"
De Blasio said Monday there is an investigation underway.
"I want to know all the facts," he said. "My heart goes out to the family. We need to know what happened."
Another 4-year-old girl, Jai'Launi's twin, along with a 55-year-old aunt and their 63-year-old grandfather, were also inside the home at the time. They were taken to hospitals, were listed in stable condition.
A firefighter who suffered a minor injury was treated and released from a hospital.
Authorities said there were no working smoke detectors in the home.
--Andrew Siff contributed to this story