“The Amityville Horror” house may still be “haunted” 50 years after the real-life massacre that inspired the book and movies, neighbors and a paranormal expert close to the case claim.

The Long Island home could still have “dormant” demonic entities inside, waiting to be reawoken and conjured anew years after the infamous 1974 murder of six family members there.

“Absolutely. I believe there are more things in this world that we don’t understand, and I don’t discount the possibility at all,” said Fran Walters, who has lived next door for the last 28 years.

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The house has long attracted curiosity seekers over its claims that it is haunted, but the legends began with a real-life crime on Nov. 13, 1974.

DeFeo rose from bed with a .35 caliber rifle in his hands and executed his parents and four siblings as they slept.

He then got dressed, and went to work. It wasn’t until hours later that DeFeo burst into a neighborhood bar and claimed somebody had attacked his family.

The next year DeFeo was sentenced to life in prison, but he spent his life blaming a long list of others — at one point reportedly claiming “voices” coming from the house urged him to do it.

Though DeFeo was believed to be a heavy drug user, famous paranormal investigators Ed and Lorraine Warren — who have since been fictionalized in “The Conjuring” series of movies — came to believe he was performing satanic rituals, and those voices may have been demonic forces he unleashed on the house.

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As DeFeo was being sentenced, George and Kathy Lutz moved into the Amityville house with their three kids at a bargain price of $80,000.

Over the next 28 days, the family claimed they were harassed by a host of terrifying happenings — including levitations and visions of hags, the children sleeping face-down just as the DeFeos bodies were found, freezing temperatures while fireplaces raged, and slime oozing from walls and doors.

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Months later the Lutzes inked a book deal to tell their story, with “The Amityville Horror: A Story,” which came out in 1977 and was an immediate success, sparking an even more successful film and sequels.

Though many wrote it off as a hoax — DeFeo’s own attorney, William Weber, later claimed he and the family concocted the story over several bottles of wine — the Lutz parents stood by their story for life.

And while the house has changed hands numerous times since the Lutzes left, none of the owners have ever reported any hauntings over those five decades — something Spera thinks doesn’t necessarily mean the Lutzes were lying, or that whatever haunted them is really gone.

“Ed used to not want to talk very much about it, because he said the more recognition you give to it, the more likely something would happen. It depends on the entity, too, that might be at that house. It may lay dormant for years,” Spera said.

“There could possibly — and I’m emphasizing the word possibly — still be something dormant in that structure that could reignite with either recognition, or somebody doing rituals in the house, incantations, or a family that is susceptible to hauntings — in other words, a family that’s weak-willed, or someone in the house that’s weak-willed.