D.C. Mayor Marion Barry told Fairfax County board Chairman John F. Herrity yesterday that the District made a mistake in not notifying the county of a riot at Lorton Reformatory Monday in which 13 prisoners were shot when corrections officers opened fire with shotguns.

The phone call by Barry, announced by Herrity and later confirmed by the mayor, was the first admission by city officials that they had erred in notifying Fairfax.

Barry also said last night that he and City Administrator Tom Downs ordered Corrections Department Director James Palmer on Friday to end a work stoppage by prison industry inmate employes at Lorton's Central facility. Monday's riot occurred after prison officials attempted to remove five inmates believed to be the strike leaders.

"I'm a pretty progressive person," Barry said. "I'm for rehabilitation and for the Lorton residents to have their rights. But I'm not for prisoners staying on strike."

About 400 inmate employes went on strike Sept. 9 protesting wages and medical services.

"It's inappropriate in that institution for the prisoners to be striking over wages," Downs said last night. "It's a privilege to work in prison, not a right . . . . There are plenty of prisoners out at Lorton who want to work."

A total of 17 inmates and two corrections officers were wounded in the melee. The five suspected strike leaders and 17 other inmates since have been transferred from Lorton, officials said.

Herrity told a reporter after his conversation with Barry, "He said they dropped the ball. He asked me to lower the profile a bit until the investigation is completed, and I agreed."

Herrity, a longtime critic of the D.C. prison in southern Fairfax County, had accused the District of deliberately misleading the county about the riot at Lorton's Central facility, which came after a 5 1/2-hour standoff between prisoners and guards.

Fairfax police have said that they were told about 3 p.m. Monday that a "peaceful demonstration" was under way at the facility, but were not notified when the incident turned violent. A pact signed by the District and the county in June requires that Fairfax police be notified of any disturbance at Lorton immediately after Corrections Director Palmer is told.

Fairfax and D.C. police officials have said they did not learn of the outbreak of violence until Tuesday.

Barry said last night that based on preliminary information, a partial breakdown of communications occurred about the time of the clash at 5:30 p.m. Monday, but he did not provide specific information.

Barry said that the extent of the District's failure will be determined by an investigation by the internal affairs unit of the D.C. police, which is interviewing corrections officers, prisoners and others involved. The unit will investigate possible criminal violations during the incident in addition to the communication breakdown, the official said.

"The citizens of the area were never in any danger," Barry said, "Nobody got close to breaking out of the place."

According to a report on the incident issues yesterday by Fairfax police, a Lorton official notified the Fairfax Emergency Operations Center at 4:15 p.m. Monday that the prison was not able to make its 4 p.m. inmate count because of a peaceful demonstration. A Lorton official called the center at 8:15 p.m. and said that all was back to normal, according to the report, but did not mention that guards and inmates clashed at about 5:30 p.m.

"In this incident . . . we were not notified until approximately 24 hours later that this demonstration had escalated to a major disturbance. This notification came about only as a result of our own inquiries."