Eleven Lorton Reformatory inmates were wounded early yesterday as guards opened fire with shotguns in an attempt to quell rioting at the Youth Center I facility that started during a power outage, officials said.

During the disturbance, inmates apparently hurled homemade firebombs at the facility's administration and academic buildings, starting blazes that burned out of control for more than two hours and gutted a wing of the academic building that had housed six classrooms.

Corrections officers fired shotguns at two groups of prisoners who charged them outside the burning buildings, according to officials. One inmate suffered serious wounds.

Fifteen separate fires were set in the two buildings, including four that were apparently started by flammable liquids, a fire department spokesman said. D.C. Corrections Department spokesman LeRoy Anderson said some of the fires were sparked by inmates "throwing things through windows, probably firebombs." He said officials did not know where or how the inmates had gotten flammable liquids.

Yesterday's disturbance, in which one corrections officer suffered minor injuries, was the latest blow to the District's troubled prison system. Facilities are severely overcrowded, corrections officials have had to scramble to avoid exceeding court-ordered population caps, and there have been a number of disturbances, including one at Lorton last September in which guards also used shotguns, wounding 13 inmates.

Anderson said the riot at the D.C.-owned Lorton complex, located in southern Fairfax County, started about 1:30 a.m. after the prison lost electric power and all the lights went off, including those used to illuminate the perimeter fence.

He said the facility's emergency power generator did not automatically begin to operate, as it should have, and was started manually about 40 minutes later.

While the 53-acre compound lay in darkness, three helicopters trained spotlights into the prison and officers and dogs from the Fairfax County Police Department surrounded the perimeter to guard against escapes, officials said.

More than 100 corrections officers clad in helmets and protective clothing and armed with shields and batons were sent to the youth center from seven other Lorton facilities, Anderson said. He said the prison was declared secure after an inmate count at 8:15 a.m.

Anderson said officers used "pepper foggers" -- shoulder-carried machines that shoot out a continuous stream of tear gas -- and fired 98 canisters of tear gas from the ground and guard towers to herd about 350 rioting inmates onto the prison's playing field about 3:45 a.m., where they were surrounded by guards and more than 40 officers from the D.C. police department's emergency response team.

Anderson said that D.C. Corrections Director James F. Palmer authorized officers to take shotguns into the facility "because there was a reasonable suspicion that life, limb and property would be in danger" during the uprising. Anderson said he did not know how many shotguns were taken inside or how many shots were fired.

Eleven inmates were injured when officers fired shotguns loaded with size 8 birdshot at two groups of prisoners in separate incidents shortly after 3 a.m., Anderson said.

He said the first incident occurred behind the administration building when inmates who charged a group of officers "were ordered to disperse and kept coming at them."

The second occurred minutes later about 100 yards away, when "50 to 60 inmates, hooting and hollering, came at another squad" near the academic building, Anderson said. He said the inmates were "not dissuaded" when the officers sprayed them with tear gas from a pepper fogger, and that the officers then fired their shotguns.

The 11 inmates were taken to D.C. General Hospital, where 10 of them were treated and released. One inmate, who was not identified, remained in stable condition yesterday with what officials described as a serious leg wound.

D.C. Department of Corrections officer Raymond Ballard, one of 22 officers who were on duty in the facility when the fracas errupted, suffered a broken sinus bone when he was attacked by inmates shortly after the lights went out in a dormitory, a Corrections Department source said.

"As soon as lights went out they just rushed him and beat him," the source said. "When lights go out officers usually move out immediately and apparently he didn't move out fast enough," the source said.

Anderson said Ballard was treated at Mount Vernon hospital and released.

Fairfax County firefighters were not allowed to enter the grounds for more than two hours to extinguish fires set by the inmates, officials said.

Six separate fires were set in the academic building, causing heavy damage to computers, typewriters and other classroom equipment. Four of the fires were started with trash and two apparently were sparked with flammable liquids, according to Anderson, who said that inmates apparently entered the building by smashing windows and possibly breaking a door.

Damage to the administration building was less severe, officials said, with seven small trash fires and two fires set with flammable liquids in and around the office of Youth Center I's administrator, Arthur Graves.

Fire officials said most of the fires in the administration building had burned themselves out by the time firefighters were allowed to enter the facility about 4:30 a.m. It took about an hour to extinguish fires in the academic building, they said. No damage estimate was available.

Starting about 5 a.m. the inmates were taken in small groups to the prison gymnasium, where they were strip-searched while officers combed the facility's four dormitories and the grounds for weapons. Sources said baseball bats, homemade knives, blackjacks and other weapons were recovered.

Corrections officials said the facility was calm yesterday afternoon, but D.C. police had been kept at the prison until about 1 p.m. while 80 inmates at Youth Center II, another Lorton facility, staged a peaceful sit-in and refused to attend classes or work programs to express "solidarity and sympathy" for the inmates at Youth Center I, officials said.

Youth Center I, a medium-security facility that houses about 400 felons aged 17 to 26 who have been sentenced under the Youth Corrections Act, was the scene of a night-long December 1983 riot and also the site of two methane gas explosions in December 1984 that forced evacuation of the facility for nine months.

In the past, Fairfax County officials have complained that District officials have not notified them of disturbances at Lorton. Richard A. King, the deputy county executive for public safety, said that officials were promptly notified about yesterday's incident.

Board of Supervisors Chairman John F. Herrity complained, however, that the county is left out of the operational decisions of Lorton but forced to respond when incidents break out. "We are the sort of the bastard not invited to the family wedding in this whole situation. We have no voice," he said.

Anderson said late yesterday that electricians had not determined what caused the power outage, but said that electricity from the main power lines had been restored "a few hours" after the blackout and that the emergency generator also had been repaired.

A Virginia Power spokesman said that the company was not informed of the electrical problem until about 7 a.m. and that a repairman went to the facility and determined that the problem was with Corrections Department equipment.

He said the repairman discovered that an "arrester," which he described as a device that acts as a shield against lightning, had blown out, which subsequently caused a fuse and other electrical equipment to go out of service. Power to the other Lorton prisons was not affected.