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A knife has been found buried on the estate of football legend and one-time murder suspect, O.J. Simpson, Fox News has confirmed.

TMZ initially reported that a construction worker found a folding buck knife buried on Simpson’s property “years ago” - possibly when the home was being demolished in 1998 - and gave it to an off-duty cop.

The cop, however, took the knife and kept it in his home for years.

TMZ reported that earlier this year, after the cop retired from the LAPD, he contacted a friend who worked in the department's homicide division. The cop told the friend about the knife and said he was getting it framed to put on his wall. He wanted his friend to get the case number for the Nicole Brown Simpson/Ronald Goldman murders, which he planned on engraving in the frame.

The friend told his superiors at the department, who demanded that the retired cop turn the knife over, which he did.

Sources also informed TMZ that authorities have chosen to keep their investigation top secret and that they have even logged the case into a computer system outside the official case file in order to keep it under wraps.

Despite all this, Simpson likely cannot be prosecuted again because of double-jeopardy laws, which prohibit someone from being charged with the same crime twice.

Watch Jonathan Hunt's report from "Happening Now" above and read the TMZ report, here.

UPDATE, 12p ET: The LAPD held a news conference to discuss the bombshell discovery. 

Captain Andy Neiman said the knife was handed over by an LAPD officer who retired in the late 90s.

It's unclear whether the officer was retired when he took possession of the knife. 

He said the LAPD doesn't know the identity of the person who originally found the knife on the property.

Neiman said at the request of investigators, he would not describe the knife in detail. 

They're still in the process of determining whether it is evidence in the more than 20-year-old murder case, he said.

The knife will undergo DNA and other testing. Neiman said they would not release the exact date that the knife was found.

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