Four .38-caliber revolvers and 24 rounds of ammunition are missing from an armory at Lorton reformatory's maximum-security facility, D.C. corrections officials confirmed last night.

The guns and the .38-caliber cartridges were taken from a cache of weapons stored in the first floor of a guard tower near the entrance to the maximum-security area that is usually accessbile only to corrections officers, according to department spokesman Leroy Anderson. He said the weapons were found to be missing during a routine check in the last two days.

"This is most unusual," Anderson said. "It is the only time I have ever known this to have happened. . . . We don't know at this point what happened to the guns."

The FBI, which has police jurisdiction over the prison complex in southern Fairfax County, is investigating the disappearance of the weapons, and a high-level D.C. Corrections Department investigation has been initiated, officials said.

One Lorton corrections officer, who asked that his name not be used, told The Washington Post that the disappearance of the guns, ammunition and 15 sets of handcuffs was reported early Monday afternoon but that no specific search of the facility for the weapons had been conducted as of late yesterday.

A corrections official said it had not been determined if any handcuffs are missing. He said regular searches of inmates' living quarters are made at each shift change and that employes submit to shakedown searches when they leave the institution, but that the guns have not been found.

The official said the disappearance of the guns is being investigated as "pilferage by the paid staff."

Most guards at the prison complex, except those assigned to watchtowers, are not armed, Anderson said. The weapons are stored in the bases of the towers -- located outside inmate living quarters in each area -- for use in case of an emergency such as an escape or prison disturbance.

Guns, ammunition and handcuffs are kept in separate lockers on the first floor of the three-level guard towers, and keys to the areas must be signed out from personnel in the tower, prison officers and officials said.

Regulations call for tower personnel to log in every time a key for the armory is removed from the tower room and the time it is returned, and corrections employes are required to be accompanied by tower guards when they enter the armory area.

All materiel in the armory is supposed to be checked in an inventory every 48 hours, corrections officers said.

The maximum-security facility, which houses more than 500 inmates, is located adjacent to the prison's Central Facility, where about 300 inmates staged a work stoppage Monday to protest stricter D.C. parole guidelines.

Anderson said the work stoppage and the disappearance of the weapons appear to be unrelated.