Authorities said the fire started around 5:30 a.m. inside a three-story vacant building at 1794 Broadway in Bushwick.
The fire was elevated to a second alarm shortly after.
MORE NEWS: Mayor sends stern letter to NYC employees: 'Report to work in person'
Citizen App video captured smoke coming from the building.
One firefighter was treated on the scene but refused to go to the hospital.
Operations on the fire remain ongoing.
This is breaking news. This story will be updated as more information becomes available.
* More Brooklyn news
* Send us a news tip
* Download the abc7NY app for breaking news alerts
* Follow us on YouTube
Submit a News Tip