A 27-year-old inmate scaled three fences early yesterday to escape from a medium-security facility at Lorton Reformatory in Fairfax County and eluded law enforcement officers, who were kept on the run all day by numerous reports of sightings.

Mark Stubblefield, serving a 36- to 90-month sentence for trafficking in stolen property, burglary and failure to appear in court, was discovered missing from the D.C.-operated facility at 4:20 a.m. during an inmate count, said Leroy B. Anderson, spokesman for the D.C. Department of Corrections.

"He went over three fences," said Anderson, adding, "You can get killed doing that." He said Fairfax County officials were notified of the escape at the prison's Occoquan I facility, and the alarm was sounded to alert nearby residents.

"It's been a zoo," said Officer Connie J. Curran, a spokeswoman for the Fairfax County Police Department. "We had a lot of people calling and saying, 'I saw the guy.' "

Curran said a Metro bus was stopped and searched on I-95, and there was a report of a sighting at a stone and gravel store. She said 18 police cars and a helicopter responded to another account of a sighting near Newington and Backlick roads after the person in question fled when approached by officers.

Police continued their search last night.

John F. Herrity, chairman of the Fairfax County Board of Supervisors and frequent critic of the District's prison, said the proper notification procedures were followed in yesterday's escape.

But he added that "the escaped prisoner running around Fairfax County" underlines, once again, the need to move the facility out of Fairfax County and into the District.

A 1,248-page consultant's study, commissioned by the county and released last fall, was extremely critical of the prison, calling it "vulnerable to attack and takeover" by inmates who often appear to be "running the place."