(CBS) New evidence has surfaced in the case of Scott Speicher, the U.S. Navy pilot shot down on the first night of the first Gulf War in 1991. Speicher was initially reported killed, but later listed as missing, his fate unknown.

CBS News Correspondent David Martin reports the new information comes from documents turned over to an American intelligence officer, who cannot be identified, by a former general in the Iraqi Air Force. After the two men examined them for three hours, the American told the Iraqi, "This brings to a close one of the great sticking points" in the 12-year saga of what happened to Speicher.

Specifically, the documents appear to solve the grisly mystery of a pound and a half of human flesh that has been at the heart of the Speicher case. The Iraqis turned those remains over to the U.S. in 1991, identifying them only as "Michael," which is Speicher's proper first name.

When the DNA did not match Speicher's, the Americans suspected the Iraqis of trying to trick them into thinking the Navy pilot was dead while they continued to hold him captive.

The U.S. was never able to identify the remains, but the documents, some of them top-secret Iraqi memos, identify them as belonging to an Air Force pilot shot down a month after Speicher.

The Pentagon will now retest those remains against the DNA of the dead Air Force pilot to finally make a positive identification.

As for Speicher, the Iraqi general insists they don't know what happened to him. Investigators have now searched more than 50 prisons, graveyards and other sites in Iraq. The most tantalizing clue turned up in a now-abandoned prison that held captured American pilots during the first Gulf war. Etched on the wall of cell 46 are the initials "MSS." Could that stand for Michael Scott Speicher? Investigators believe those initials were scratched there in the last two to three years. They are still trying to figure out what the other letters on the wall might mean.

The search team went over every square inch of the cell looking for some other piece of evidence Speicher was here. They even went into the toilet area and scrapped the drains for his DNA.

It will take months of testing to see if any of the samples match Speicher's DNA. In the meantime, the search goes on. Investigators have already dug up six graves where he might have been buried, but none of the bodies had caps on their front teeth like Speicher had. The investigators are coming back to this cemetery on Saturday to dig up another body.