CHEYENNE, WYO., OCT. 28 -- Air Force officials parked an armored car on top of a Minuteman 3 silo in 1984 when a computer malfunction indicated that the nuclear-tipped missile was about to launch itself from the underground silo, it was reported here today.

The episode occurred at Warren Air Force Base near Cheyenne on Jan. 10, 1984, when computer lights seemed to show the 60-foot missile was preparing to go into a launch sequence, the Casper Star-Tribune reported.

"Security police did respond with a vehicle that was parked on the missile silo," said Maj. Fred Harrop, a Strategic Air Command spokesman. "This is an available precaution until the source of the erroneous light could be determined."

Harrop said, "There is absolutely no way a Minuteman 3 missile could be accidentally launched . . . . There was never any possibility of an inadvertent launch as redundant safety measures exist to prevent such an occurrence."

But Harrop could not explain why the Air Force took the precaution of driving a truck on top of the silo if there was no chance of a launch.

SAC officials said blinking lights on a computer panel were a false alarm caused by a problem in the intercontinental ballistic missile's guidance system and that the three-warhead Minuteman 3 could not have launched itself because of safeguards.

Officials said the crew at the missile silo realized that the Minuteman could not launch itself, but called a safety team immediately when the computer indicated something was wrong with the missile.

"The computer constantly asks the missile questions on readiness and, in this case, the computer got an answer that wasn't right," an Air Force spokesman said. He said the nuclear warheads on intercontinental missiles are not armed until after they are launched and that the three warheads on the Minuteman were not armed at the time of the incident.

The Minuteman has a range of more than 6,300 miles and is being partially replaced in the U.S. land-based nuclear arsenal by 10-warhead MX nuclear missiles. The first MX missiles went on alert last year.