Firefighters worked for hours after smoke became flames outside a seven-story building.
EAST WILLIAMSBURG, N.Y. — Firefighters battled a stubborn underground fire in Brooklyn early Wednesday after reports of carbon monoxide inside a residential building led to a large evacuation and at least two people were taken to the hospital, officials said.
The incident unfolded on Humboldt Street as crews responded to a complaint that initially sounded like a routine safety check. Instead, officials said, dangerous conditions spread quickly from underground utility spaces to the street, forcing residents out of a seven-story building and prompting a long operation to control heat, smoke and residual gas below ground. The cause was under investigation, and officials said winter conditions could have played a role in damaging underground infrastructure.
Firefighters were called about 3:30 a.m. after reports of smoke rising from a manhole near 101 Humboldt St., and officials said crews soon detected high levels of carbon monoxide inside the building. As firefighters investigated the source, conditions worsened and the response escalated, with officials describing a situation that developed into a gas leak concern. “During the winter months with the salt on the ground, we do get the electric utilities get affected,” FDNY Battalion Chief Barry Leguernic said, adding that work was underway to determine whether compromised wiring contributed to the initial problem.
Residents streamed out as firefighters moved through hallways and common areas, checking air levels and urging people to leave quickly. Officials said more than 200 residents were evacuated from the seven-story building. Medics transported at least two people to a hospital, though officials did not immediately describe the extent of their injuries. Outside, firefighters kept lines trained on nearby structures to prevent the heat from spreading and to cool the street and parked vehicles as the underground fire intensified.
By about 5:15 a.m., smoke on the street turned into open flames and scorched two parked cars, according to officials. The fire was described as shooting out of a transformer vault, a space that can connect electrical equipment to underground distribution. Firefighters worked to isolate hazards below street level, and officials said crews were able to turn off valves feeding an underground gas line. Even after that step, the operation remained difficult because residual gas and heat can linger in confined underground spaces, requiring careful venting and continued monitoring before the area can be considered safe.
The long duration of the response highlighted the challenges of underground utility fires in dense neighborhoods, where manholes, transformer vaults and gas lines sit close to building foundations and sidewalks. Unlike fires inside a single apartment, underground incidents can move unpredictably through connected chambers, sending smoke into basements, lobbies and utility rooms. Officials said investigators were working to determine what sparked the fire and were also looking into weather-related factors. Leguernic said winter conditions can increase strain on systems, both from salt and from the heavy electrical demand that comes with cold weather.
For residents, the most immediate concern was the carbon monoxide report that prompted the initial call and the speed with which conditions changed. Ruben Burgos said he drove about two hours to check on his 80-year-old father after learning about the evacuation. Burgos said what bothered him was that carbon monoxide detectors inside the building did not appear to alert residents during the emergency. “One confusing thing to me was everybody has carbon monoxide tests, not one went off in the building,” Burgos said. Another resident questioned whether the building would be safe if conditions like this returned, calling carbon monoxide “a silent killer.”
As firefighters continued to work, the American Red Cross assisted evacuees, officials said, helping residents who needed temporary support while the building was cleared. Authorities said the operation lasted hours, and FDNY crews worked to gain control while preventing flare-ups and checking air quality before residents could return. Officials did not immediately say whether Con Edison equipment was damaged, whether utilities were interrupted beyond the immediate area, or whether the building would require repairs before normal operations could resume.
By Wednesday afternoon, officials said the fire had been brought under control after roughly seven hours of work, and investigators were still reviewing what triggered the underground blaze and how the carbon monoxide entered the building. Authorities said additional information would be released as the investigation continues.
Author note: Last updated February 19, 2026.