O.J. Simpson's name is back in the news for a fascinating story that creates more questions about whether the former NFL running back was responsible for the 1994 murders of his ex-wife, Nicole Brown Simpson, and Ronald Goldman.

Law enforcement sources told TMZ that a construction worker found a knife buried on the perimeter of Simpson's former mansion and that it's currently being tested by the Los Angeles Police Department in a top secret investigation. TMZ reported the story early Friday morning, but the knife reportedly was discovered years ago -- with TMZ hearing anywhere from "several years ago" to 1998, when the estate was demolished.

The construction worker reportedly brought the knife -- a folding buck knife -- to the street, where he saw an LAPD officer, who took the knife after being told where it was discovered. But the cop, who was off-duty at the time, kept the knife for years rather than turn it in, sources told TMZ.

That cop, who since has retired, reportedly contacted a friend who worked in the LAPD's Robbery Homicide Division (RHD) in late January and told him about the knife, saying he intended to get it framed and that he wanted the departmental record number for the Brown Simpson/Goldman murder so it could be engraved on the frame. The friend reportedly wasn't too thrilled about the request and told his superiors, who demanded that the retired cop turn over the knife. He did.

The knife currently is being tested for hair and fingerprints, and it will be tested for DNA and other biological evidence next week, sources told TMZ. One source told TMZ that cops who eyeballed the knife think it could have blood residue on it, though it's hard to tell for sure because it's so rusted and stained.

This obviously is a bizarre story. And sources told TMZ that since Simpson was found not guilty for the 1994 murders of Brown Simpson and Goldman, it's still an open case, though the Hall of Fame running back can't be prosecuted again because of double jeopardy.

Simpson currently is serving a 33-year sentence in a Nevada prison for numerous felonies, including armed robbery and kidnapping.