Inmates at Lorton Reformatory's Occoquan I and II facilities threw beds out of dormitories and set mattresses afire yesterday after corrections officials tried to place additional beds in dormitories that inmates and corrections sources say are overcrowded.

No one was injured in the 2 p.m. incident, when officers placed two new beds in each of 13 dormitories at the Occoquan facilities.

Corrections Department spokesman LeRoy Anderson said "a handful" of inmates threw 10 beds out of the dormitories and set three mattresses on fire. The fires were extinguished by officers and two new beds were later added to each of the dormitories, he said.

Anderson said he did not know why the inmates rebelled. He said the prison is not overcrowded because "it has no court-ordered population cap." He refused to provide population figures.

A source at Occoquan said the new beds were the first phase of a plan to add 10 beds in the dormitories by "double bunking" them.

The two Occoquan facilities are the city's only prisons for adult felons that do not have court-ordered population limits, and in recent months they have been used to house overflow inmates from facilities under court order, such as Lorton's Central facility.

According to department records filed in U.S. District Court, the combined population at the two Occoquan facilities last Tuesday was 1,259 inmates, or 373 more than capacity. The records show that the population at the two facilities has grown by more than 200 inmates since January, when the Justice Department stopped taking newly sentenced city inmates into federal institutions.

Alexa Freeman, an attorney with the American Civil Liberties Union's National Prison Project, said about 20 inmates had complained to the project about conditions at the Occoquan facilities. She said ACLU lawyers hope to visit there next week to decide whether to seek court-ordered population limits for them.