Loudoun County sheriff's deputies arrested a West Virginia man yesterday and charged him with murder in the slaying of Judith L. DeMaria, who disappeared two years ago while jogging on the Washington & Old Dominion bicycle path near Dulles International Airport.

Charles Curtis, 28, whom deputies described as a transient from Martinsburg, W.Va., was arrested a few hours after officials uncovered the remains of a badly decomposed body in a shallow grave about a mile from where DeMaria was last seen. Curtis, who deputies said lived in the Washington area off and on, was arrested at the site and charged with first-degree murder.

FBI officials and sheriff's deputies were unable to determine by last night whether the remains were those of a male or a female, but deputies said they charged Curtis with DeMaria's death based on his statements to them and on unspecified evidence.

DeMaria, 27, a tennis instructor at the Capitol Courts Racquet & Fitness Club in Sterling, disappeared Aug. 2, 1985, during a late-morning jog on the W&OD path. She was last seen near a bridge that crosses Broad Run Creek. The day after her disappearance, deputies found what one described as "a substantial amount of blood" in a nearby field; tests showed the blood could have been hers.

Officials said yesterday that on Wednesday night Curtis contacted a Loudoun sheriff's deputy who had arrested him years ago in an unrelated case and began giving information that led to his being charged with DeMaria's death.

Officials would not give specifics on what he told them or say how they were able to find the grave around midnight in a heavily wooded area.

It was not known whether Curtis knew DeMaria. Investigators said last night his name had come up previously in connection with the case, but they would not say he had been a suspect before yesterday. Before the arrest police had said they had their eye on another man from this area who had known DeMaria.

An extensive search was made of the area where the grave was found, north of Rte. 634 and west of Rte. 28, and the body was not removed until 8:15 p.m. It will be taken to the Northern Virginia medical examiner's office in Fairfax for autopsy.

DeMaria's family, which has been kept informed of developments in the case over the last two years, was notified yesterday morning that "some human remains" that might be Judith DeMaria's had been found, according to her stepmother, Martha Whitestone.

"Of course it's a shock. We'll all feel better once we know officially," added Whitestone, who works for United Airlines, as does DeMaria's father John.

Because the remains are so badly decomposed, it was not known how long the autopsy would take, according to Lt. Greg Stocks, a spokesman for the Loudoun County Sheriff's Department.

For two years, investigators have followed leads in the search for DeMaria. A $5,000 reward was offered; psychics called police with tips; orange posters with DeMaria's photo on them dotted the county, and hundreds of volunteers searched for clues.

For one man, Robert E. Turner, then a Loudoun County deputy sheriff and now a corporal with the department, the case has become something of a personal crusade. He has carried DeMaria's image with him in his dreams and in his pocket, where he keeps her driver's license in case someone can identify her photograph. For Turner and the other investigators, there was a feeling of wanting to put the case to rest.

"Last night when we found the body it was an enormous relief," Loudoun County Sheriff John Isom said yesterday afternoon in a brief news conference at the site where the body was found. "We had put a lot of hours into this case."

Curtis, who has been convicted of grand larceny and armed robbery, was being held without bond last night in the Loudoun County Adult Detention Center in Leesburg. A preliminary hearing in the murder case was set for Oct. 1.