A massive fire at a waterfront warehouse in Red Hook flared up again Thursday afternoon, with smoke restarting from the roof and firefighters briefly turning the hoses back on before standing down to monitor hot spots.

Two firefighters have minor injuries, officials said.

The blaze began around 11:25 p.m. at 481 Van Brunt St. and climbed to a fifth alarm by 2:33 a.m., bringing more than 250 FDNY and EMS members.

FDNY Chief of Operations Kevin Woods said crews arrived in under three minutes to find heavy fire on the second, third, and fourth floors and through the roof. Because of the danger, firefighters pulled out and fought from the exterior, using large-caliber streams from the street and Marine 9, the department’s fire boat, from the bay. FDNY also used drones with thermal cameras to spot hot spots and guide where to put water.

The warehouse—built in 1870 with heavy-timber construction—sustained extensive damage, including a roof collapse and a partial fourth-floor collapse, according to FDNY. Structural engineers must evaluate the building’s stability before investigators can safely go inside to determine the cause.

As of midday, fire investigation units remain on scene, Van Brunt Street near the warehouse is restricted, and operations are ongoing. Officials say flare-ups like this are not unusual after a fire of this size.