The Air Force confirmed Wednesday an MX nuclear missile fell in its underground silo in Wyoming June 16 and was removed for repairs but that all missiles returned to full operational capability Dec. 30.

The Air Force, however, declined to confirm or deny a Washington Post report that the incident prompted the military to remove nuclear warheads from four more of the $80 million strategic missiles.The Post, quoting unidentified Defense Department officials, said the Air Force's decision to remove the 50 warheads - each MX has 10 - was made to prevent additional damage to the weapons.

Air Force Capt. Liz Lane-Johnson, deputy chief of public affairs at F.E. Warren Air Force Base near Cheyenne, Wyo., where 50 MX missiles are deployed, confirmed by telephone that a "key electrical disconnect" led to one of the missiles slipping down into its silo last June.

Investigators found the 70-foot long, 90-ton missile had fallen between 6 inches to 1 foot, causing damage severe enough to require that it be removed and returned to the manufacturer for repairs.

"There was no danger of an accidental launch or anything like that," Lane-Johnson said. "The incident was extensively investigated, the four stages of the missile were removed from the silo and sent back to the contractors" for repair.

"The missile is now intact," she said. "The Peacekeepers (MXs) reached full operational capability on Dec. 30," she said.

As to whether the warheads of four other MX missiles were removed after the incident, Lane-Johnson declined comment. "We don't discuss day-to-day alert status of missiles," she said.

An Air Force panel, chaired by Lt. Gen. Richard A. Burpee, commander of the 15th Strategic Missile and Bomber Wing, concluded the problem was not the result of sabotage but from improper production of a single group of five missiles, the Post quoted sources as saying.

Senior Air Force officials responded to the panel's findings late last year, secretly ordering that the 10-warhead top of each of the five missiles be removed, the Post said.

Rep. Les Aspin, D-Wis., chairman of the House Armed Services Committee, complained last week in a private letter to Gen. Larry D. Welch, the Air Force chief of staff, that at a January conference, Air Force briefers did not accurately describe the missiles' status.

Aspin's letter, a copy of which was obtained by The Post, called the Air Force claim of 50 fully operational missiles last December "confusing at best and misleading at worst" given that some "missiles lack warheads."