Sign up for our COVID-19 newsletter to stay up-to-date on the latest coronavirus news throughout New York City

Two Williamsburg waterfront warehouses burned down last year after firefighters failed to extinguish burning embers from a smaller blaze there hours earlier, according to two long-awaited reports acquired by this paper.

The reveal comes on the heels of a lawsuit that also alleges the Bravest made things worse by shutting off the water supply to the entire building after the first fire, so sprinklers were out of order when the fire reignited.

The reports — which investigators signed off on on Jan. 8, despite department reps insisting the investigation was ongoing for weeks afterward — finally provide some answers about the massive inferno that blazed through two CitiStorage warehouses on Jan. 31 last year, which neighbors and victims have been demanding from fire brass for months.

According to the first report, a light fixture triggered the initial fire at one warehouse on N. 11th Street at 4:29 am, igniting some cardboard boxes in a metal storage rack, then spreading up a wood pallet and through stacks of boxes across several levels of the building.

The report does not say how the first flames were subdued — indeed, it does not say they were subdued at all — but the initial incident report says the warehouse’s sprinkler system controlled the flames and firefighters then doused the smouldering debris.

A suit from storage outfit Recall Holdings, one of the companies using the warehouse, claims the firefighters then turned off the water to the entire property’s sprinkler system — making it inoperable — instead of simply blocking off the handful of sprinklers activated by the small fire.

The crews then finished their work at 5:45 am, according to the initial incident report.

The fire then reignited at 6:28 am, according to the second department report, and the conflagration spread through the N. 11th Street warehouse — including the thousands of government and other documents it contained — then on to the neighboring N. 12th Street warehouse where building owner Norman Brodsky and his wife Elaine lived at the time.

The report, which states the second fire was “confined and extinguished,” cites the cause of the blaze only as “brands” — burning material left over from a previous fire.

Brodsky recently filed a $3-million lawsuit against Recall and a second tenant, CitiPostal, over the loss of his home and belongings on Jan. 15, claiming the storage companies were responsible for maintaining the space and therefore the pyre that engulfed it.

But Recall’s $50-million suit, filed on Jan. 29, points the finger at the Fire Department, claiming it screwed up both by turning off the entire sprinkler system and failing to fully extinguish the first fire.

A department spokeswoman claimed that the firefighters were just following protocol, and the sprinklers were the building’s responsibility.

“It is necessary for the fire department to completely deactivate the system, and it is the facility’s responsibility to call the sprinkler company to reactivate,” said Elisheva Zakheim.

Zakheim also claimed the firefighters did fully extinguish the initial flames and denied the connection between the two fires, saying they are separate incidents that occurred 15 to 20 feet apart in a very large warehouse.

“The firefighters followed protocol and proceeded to extinguish the fire completely,” she said.

The rep also claimed the report detailing the incidents — which are marked as “case closed” — are not finalized and that investigators are still looking into potential causes of the second blaze. She later e-mailed to say the cases are, indeed, closed.