Extreme crowding has created a "very explosive situation" at a Lorton Reformatory facility where an inmate disturbance was quelled with tear gas Friday night, corrections officers charged yesterday.

The tense situation at Youth Center No. 2, which has a capacity of 250 but now houses 440 to 450 prisoners, can be defused only by adding guards or moving some of the 190 inmates transferred there last week after methane gas explosions at another facility, they said.

Officials of the corrections officers union also reported a minor disturbance Friday night at another Lorton facility to which inmates were transferred Thursday. Lorton, a sprawling complex of six District facilities, is in southern Fairfax County.

The additional inmates at both facilities were among 399 evacuated Thursday from Youth Center No. 1 after the facility was deemed uninhabitable because of a methane leak. The source of the leak, which is blamed for separate explosions Monday and Thursday that severely burned two inmates, has not been pinpointed.

Officials of the D.C. Department of Corrections say they do not know when prisoners can be returned to Youth Center No. 1. A fire department official investigating the leak said "it's going to be a while" before its testing is complete.

"They're not going to be able to keep them there long," said Dorothy Donnelly, staff assistant of the American Federation of Government Employees, Local 1150, referring to about 140 of the transferred inmates who are being housed in the gymnasium of Youth Center No. 2.

"They need to do something about it now. The security is very poor. We don't have enough officers for that type of thing," Donnelly said.

Donnelly and other union officials said the security problems include "inadequate" equipment and rivalries between inmates of the two youth facilities, both of which house felons aged 17 to 26 who are sentenced under the Youth Corrections Act.

James Palmer, director of the D.C. Department of Corrections, has said that he may ask the Federal Bureau of Prisons to accept some Lorton inmates as a means of relieving Lorton's crowding. He could not be reached for comment yesterday.

The second inmate disturbance Friday night occurred at the Occoquan detention facility, where "a little gang fight" broke out in a dormitory between transferred inmates and prisoners already at Occoquan, according to J.D. Lewis, a union staff assistant. One inmate was put into protective custody and another was placed in isolation as a result of that incident, he said.

Occoquan, which had been at its capacity of about 900 inmates, received 122 additional inmates because of the transfers, officials said.

The disturbance Friday at Youth Center No. 2 was sparked by a proposed change in inmate visiting hours at the facility.

According to Lewis, the incident began shorty after 9 p.m. Friday when a group of inmates from Youth Center No. 2 went to the gymnasium, where 140 inmates from Youth Center No. 1 are being housed, to ask them to join in a protest of crowding.

The prisoners in the gymnasium felt threatened and locked the gym's doors, Lewis said, and the inmates on the outside began to congregate in a large yard nearby.

They were soon joined by some inmates from inside the gym, swelling the size of the gathering to about 100, and "little scuffles took place," Lewis said.

Lewis said that a tower officer, concerned by the size and temper of the crowd, was unable to determine exactly what was going on because the towers are not equipped with spotlights. The officer shot flares so he could better see what the inmates were doing, Lewis said.

The officer then shot several tear gas canisters in an attempt to defuse the situation, Lewis said, but the tear gas had lost its potency because of age and had no effect.

When armed Fairfax County police showed up on the perimeter of the facility, Lewis said, "the inmates had a change of heart" and soon returned to their dormitories.

Correction officials who did not want to be identified said that corrections officers fired tear gas at a group of 100 inmates who tried to storm the gym, and that the gas turned them away