A massive blaze at the NYPD’s Brooklyn impound warehouse appears to have been accidental, sources told The Post Wednesday — as officials began to assess the potential damage to decades of evidence stored at the facility. 

The FDNY said that while the fire was brought under control at around 6 p.m. Tuesday, it was still on the scene in Red Hook Wednesday morning “handling fire flare-ups and hot spots” before finally being able to enter the site later in the afternoon.

It’s not yet clear what exactly caused the inferno that engulfed the Erie Basin Auto Pound in Red Hook, but police sources told The Post that it did not appear to be criminal in nature. 

The facility is used by the NYPD to house a variety of evidence dating back to the 1980s, including seized vehicles and motorcycles, and “historic vehicles” tied to past cases.

“To preserve the evidence in that building is going to be difficult and until the detectives from the arson and explosion unit get in there and see the damage we won’t have any determination,” Paul DiGiacomo, head of the NYPD Detective Endowment Association told Fox5 News on Wednesday.

“I don’t know if it was lost,” DiGiacomo said of potential damage to evidence. “That’s yet to be determined. Again, a lot of that information is backed up on the computer systems.”

The three-alarm blaze broke out shortly after 10:30 a.m. Tuesday, sending huge plumes of smoke into the air as more than a dozen employees inside the facility fled to safety, cops said.

Fire investigators are considering the possibility that lithium batteries from e-bikes stored at the site may have sparked the blaze, although sources said the batteries are disconnected from the bikes and that the fire began elsewhere in the warehouse.

Among the “historic vehicles” stored at the site are the patrol cars of fallen cops, including the cruiser where NYPD detectives Wenjian Liu and Rafael Ramos were gunned down last year, and the squad car hero cop Edward Byrne was sitting when he was killed in 1988.

According to sources, the potential loss of evidence would most likely impact cold cases — or possible future appeals. Evidence tied to pending or active cases is not stored at the warehouse, the sources said.

The department stores more than 1,000 barrels of evidence, dating back decades, that includes DNA pulled from clothes and other items at the warehouse.

Much of it — including DNA — is backed up on computer files or with photographs, as was the case when Hurricane Sandy damaged some NYPD evidence there, sources said.

The massive 2012 storm, which ravaged the region, damaged the NYPD facility and ruined troves of evidence stored there.

After Sandy, provisions were announced to prevent future damage to the items kept at the site, but it’s unclear if those measures were ever taken.

Most, if not all, of the items stored there during Tuesdays’ fire date to criminal cases prior to 2012, and have been tested and photographed so have likely not been lost forever, sources said.

However, full details on the evidence stored at the site are not known, nor has the damage, if any, yet been determined, the sources said.

Additional reporting by Reuven Fenton