The deadly blaze, which broke out early Wednesday at NYCHA's Patterson Houses in the South Bronx, was started by an a lithium-ion battery on an electric bike, which was blocking the apartment's exit, officials said.

This story has been updated since original publication.

A fire that killed an 11-year-old boy in a NYCHA apartment building in the Bronx was caused by a lithium-ion battery on an electric bike, officials said—renewing concerns about the potential dangers of such devices, which have contributed to hundreds of similar blazes across the city this year.

The fire broke out early Wednesday morning in the kitchen of an 11th-floor apartment at NYCHA's Patterson Houses in Mott Haven. While FDNY crews arrived within four minutes, the e-bike that caused the blaze "was placed in the pathway of the exit door," according to Fire Commissioner Lillian Bonsignore, and "made it impossible for the residents to leave safely."

Kristina Diaz, a resident of 35 years who also lives on the 11th floor and serves as the development’s captain of tenant patrol, described hearing neighbors banging on doors down the hall shortly before 1 a.m. on Wednesday, and said by the time she got to her front door, "the whole kitchen and living [room] was already smoky."

She then watched firefighters break down the door of the blazed apartment, and described seeing one of the residents on the floor.

She said she received 72 calls in 18 minutes from fellow neighbors asking what happened, or inquiring about how they could help. "I don’t want nothing, just bring a candle for the little 11-year-old," she told them.

Wednesday's blaze is the second fire residents of Patterson Houses experienced this year, following an electrical fire that occurred in January and injured six .

Residents of the building expressed shock and grief. Florence Banks, 68, lives on the fifth floor and said she was watching TV when she heard firetrucks pull up to the building. She called her neighbor, and watched from the hallway windows as firefighters "were bringing people out, and pumping their chests."

"I couldn’t take that," she said. "I’m just shocked."

Officials said the damage was contained to the apartment where the fire started. In addition to the boy who was killed, four others were critically injured, including two teenagers.

"Today is a horrific reminder of the danger that lithium-ion battery fires can pose," Mayor Zohran Mamdani said at a press conference outside Patterson Houses on Wednesday, where officials displayed the charred e-bike that ignited the blaze.

The city has seen more than 400 fires caused by lithium-ion batteries so far this year, officials said, up from 292 last year, and six New Yorkers have died in 2026 so far.

According to the FDNY, 22 of those fires this year took place in NYCHA buildings—up from 18 such fires in 2025, and 13 in 2024.

E-bikes have become increasingly popular in recent years, especially among residents who work as delivery drivers. But the batteries they run on can spark fires that are "extremely dangerous, because they spread fast and ferociously," Bonsignore said.