A knife found buried under O.J. Simpson’s former Los Angeles estate where he lived at the time of the murders of Nicole Brown Simpson and Ron Goldman is undergoing forensic testing, Fox News confirmed Friday.

TMZ reports a construction worker found the knife years ago and gave it to an off-duty cop who kept it in his home before finally turning it over to police in January. TMZ did not specify when the knife was found, but reported that it may have been around the time the home was destroyed in 1998.

"It is being treated as we would all evidence," LAPD Capt. Andy Neiman said Friday. He added that police were "quite shocked" to learn about the knife after so many years.

Simpson's property was in the Brentwood section of LA. In 1995, a jury found him not guilty of murder after the so-called "Trial of the Century" dominated the media for months. Nicole Brown Simpson and Ron Goldman, her friend, were found stabbed to death in June of 1994.

In 1997, a jury found Simpson civilly liable for the slayings. He's now imprisoned in Nevada on a robbery-kidnap conviction.

The weapon used in the killings has been a mystery for decades.

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Law enforcement sources told TMZ the blade is a folding Buck knife. It's now being tested for hair and DNA after it was handed over to the LAPD’s Robbery and Homicide Division.

NBC News, citing unnamed law enforcement officials, reported

that it was a smaller, relatively inexpensive utility-style blade typically carried by construction workers or other laborers and inconsistent with it being the murder weapon.



"We discovered it and our investigators immediately followed up on it," Neiman added. Simpson likely cannot be prosecuted again for the stabbings because of constitutional protections against being charged for the same crime twice, or double-jeopardy.

One source told TMZ the knife appeared to have blood residue on it, but it’s extremely rusted and stained, requiring further testing.

A member of Simpson's legal "dream team" in his murder trial called the find "ridiculous." Attorney Carl Douglas told the Los Angeles Times, "It's amazing how the world cannot move on from this case!"

The cop who kept the knife, an officer assigned to the traffic division, was off-duty at the time and never alerted higher-ups to the discovery, TMZ reported.

In late January the cop reportedly contacted a friend in the homicide division and told him he was getting the knife framed for his wall.

According to TMZ, the cop even asked his friend to get the department’s record number for the Simpson-Goldman murder case so he could engrave it in the frame. He was forced to surrender the knife to LAPD when the friend told superiors.

Sources told TMZ authorities are keeping their investigation top secret and under wraps, even logging the case into a computer system outside the official case file.

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The Associated Press contributed to this report.