Two Fairfax County supervisors, a state senator and angry county residents yesterday demanded that the D. C. government take immediate action to alleviate crowded conditions at the city-run Lorton Reformatory.

"It's a powder keg waiting to go off," said Marsha Hanson, president of the Lorton Federation of Civic Associations and organizer of the emergency neighborhood meeting that was announced from the pulpits of many churches in the area yesterday. Hanson's group represents 13,500 Lorton area residents. "It's unfair that we have to worry about a city problem."

"Ship them the inmates back to the city. We are tired of being dumped on by everybody," said Robert C. Magor, president of the Newington Civic Association. Newington is a largely residential area in southern Fairfax County near the Lorton correctional complex.

The residents' latest complaints were triggered last week by the temporary closure of the facility's Youth Center No. 1 following two explosions there that may have been caused by methane gas seeping from a nearby county landfill. Two inmates were severely burned in the explosions, and nearly 400 others assigned to the center were shifted to other sections of the prison.

About 190 were transferred to Youth Center No. 2, which has a capacity of 250 but now houses about 450, and corrections officers had to use tear gas Friday to defuse a disturbance there that officials said was touched off by crowding.

A second, apparently less serious disturbance occurred the same night at the prison's Occoquan facility -- one of six that comprise the complex -- after 122 inmates from Youth Center No. 1 were shifted there.

"We get the county's garbage," said Magor, referring to the county-run landfill near the prison, and "we get the city's prisoners."

The residents, fearful that another gas explosion could be imminent, demanded yesterday that safety measures be implemented to ensure that a similar gas leak does not occur.

John F. Herrity, chairman of the Fairfax County Board of Supervisors, told those gathered in Lorton's Lenny Skutnik Community Center yesterday that he will give the D.C. Department of Corrections "a couple more days" before the county initiates a lawsuit to force it to move the prisoners. The crowding violates a legal agreement between the county and the city, Herrity said. Supervisor T. Farrell Egge (R-Mount Vernon) also attended the meeting.

James Palmer, District corrections department director, said Friday that he may ask the Federal Bureau of Prisons to accept some Lorton inmates. He could not be reached for comment yesterday.

Until the cause of the explosions is determined and the facility declared safe, officials said, Youth Center No. 1 cannot be reopened. Prison officials said they are not sure how long that process will take.

State Sen. Joseph V. Gartlan (D-Fairfax) said he will join the county's effort to pressure the city to remove some prisoners from Lorton. "It's too dangerous a situation for any one of us to ignore."

The Rev. Carl O. Stewart, pastor of the Cranford United Methodist Church in Lorton, informed his congregation of yesterday's meeting and attended along with about 65 other area residents. "We want to know what is being done."