Foul play is suspected in the disappearance of a 39-year-old Southeast Washington woman who has been missing for almost three weeks, D.C. police said yesterday.

Police said Barbara Jean Dreher, a secretary with the D.C. public school system for 15 years, was last seen by her daughter on Aug. 12. Dreher's car was found abandoned outside a Southwest apartment building Monday, police said.

Dreher, a mother of five who lives at 3030 30th St. SE, drove to the home of her 19-year-old daughter about 5 p.m. on Aug. 12, according to Dreher's sister, Gwendolyn Bell.

Dreher dropped off her 6- and 9-year-old sons at the daughter's home, saying she was going to pick up some money and would be back shortly, Bell said. Dreher then drove away in a 1980 burgundy Oldsmobile Cutlass and has not been seen since.

Dreher was not reported missing until nine days later, police said. Bell explained yesterday that her sister sometimes stayed for long periods of time with her estranged husband in Hillcrest Heights.

According to police investigating the disappearance, a relative of Dreher's, whom they declined to identify, spotted a man driving her car last Monday and followed him to a Southwest apartment building, where the man parked the car and got out.

The family member immediately notified police and identified the man when police arrived, sources said. They said the man denied driving the car and claimed not to know Dreher. Since the car was not reported stolen, sources said, the man was not taken into custody.

Police said they impounded the car. Certain "items" that are believed not to belong to Dreher were found in the car, police said, but they declined to be more specific.

Bell said she talked to her sister two days before she disappeared, and there was no indication she was in any kind of trouble.

"She has all those kids, and we're all very concerned about how they're going to be taken care of," Bell said.

Dreher was described by police as a black woman, 5-feet-2, 130 pounds, with brown eyes, black hair and a medium complexion. She was last seen wearing a green shirt and white slacks. Police ask that anyone with information about her disappearance call 576-6772.