Dallas ? Archivists are trying to preserve and copy the only known sound recording of the gunshots that killed President John F. Kennedy — a recording that has fueled conspiracy theories.

The recording, made by a police motorcycle radio, is now too fragile to be played and has never been authentically copied, officials said. Researchers at the National Archives in Washington hope optical scanning will help.

The recording became a focus of a 1979 report by the House Select Committee on Assassinations.

Committee members said it indicated four shots were fired at the Dallas motorcade on Nov. 22, 1963, including one from a separate location from where Lee Harvey Oswald fired shots, suggesting more than one shooter. The committee concluded that Oswald probably did not act alone.

The recording was not used during the Warren Commission investigation, the first government inquiry into Kennedy’s assassination. The commission concluded Oswald was the lone gunman and fired three shots.

For years researchers have studied inferior copies of the recording.

Some say the recording reveals three shots were fired and Oswald acted alone; others say they can hear four shots and conclude Oswald was aided by a second gunman.

Gary Mack, curator of the Sixth Floor Museum at Dealey Plaza, near where the shooting took place, said an authentic copy of the recording might “resolve part of the Kennedy assassination, one way or the other.”

“There is not closure on this issue,” Mack told The Dallas Morning News’ online edition Monday.