Just in Time for the New OJ Movie

A construction worker found a knife buried on the perimeter of the former O.J. Simpson estate ... and it's currently being tested by the LAPD in a top secret investigation ... law enforcement sources tell TMZ.

The story is incredible. We're told a construction worker found the knife years ago -- we have heard several different stories, ranging from "several years ago" to 1998, when the house was demolished.

The weapon is a folding buck knife.

Our law enforcement sources say the construction worker took the knife to the street, where he saw an LAPD cop. He told the officer where he found the knife and the cop took it.

Turns out the cop -- who worked in the traffic division -- was off duty at the time, working security for a movie shoot at a house across the street on Rockingham. Our sources say the officer took the knife home and kept it ... kept it for years.

  TMZ

...but hey, do what you want...you will anyway.