The D.C. Health Department is investigating an incident in which a 4-year-old boy walked out of an after-school program at Burroughs Elementary School in Northeast Washington, got on a bus and rode around the city for several hours before he was discovered by the driver and returned to his anxious family.

The director of Scoobies Before and After Care Program, Calvin Moore, said the aide in charge of the youngster's group was immediately suspended for two weeks without pay after the Jan. 10 incident and will be placed on 90 days' probation upon his return.

The child, Aaron Kates, a pre-kindergarten student at Burroughs, was unharmed and seems to have treated the mishap as a lark, said his mother, Yolanda Kates.

"It was an adventure. He doesn't have a clue as to how traumatic it was," said Kates. "He kept asking me why was I crying."

The Kates family lives around the corner from Burroughs, and a grandfather usually picks up Aaron and his sister, 8, around 5 p.m. Family and school officials believe that at about 4:45 p.m., the boy saw a man he thought was his grandfather and followed him out the front door, which automatically locks from the outside at 4:30 p.m.

Kates said her son told her he crossed the street, started speaking to a woman at the bus stop and followed her onto the G8 bus. He fell asleep and woke up to find only the bus driver, who called transit police. By then, D.C. police already had received a missing child report from the school. He was reunited with his parents about 7:45 p.m.

Director Moore said the incident occurred during the "transition time" when the program switches from homework assistance and tutorials to recreational activity, and the aide in charge of Aaron's group left the children to get basketballs out of a closet.

The program aide, identified as Donald Harris, 32, "had been a model employee until this one incident occurred," said Nae Davis, the principal at Burroughs, where Harris is also an education aide. He has worked at Scoobies for 10 years and at Burroughs since October, according to Moore and Davis.

The suspension from the after-care program, Davis said, did not affect Harris's employment at the school. In fact, the day after the incident he was tapped to work as an "emergency" substitute teacher when the regular teacher had to leave because of an emergency with her own child.

A spokeswoman for D.C. schools did not return several calls seeking comment on the use of Harris as a substitute teacher.

The city's Health Department licenses day-care centers, but privately funded after-care programs such as Scoobies are not licensed. The agency, however, is looking into the incident because it received a complaint and because "we are concerned about the public health and safety of all residents," said Norma Stewart, acting administrator for its licensing regulation administration.

Moore said a Health Department inspector who interviewed him last week said that, depending on the findings, Scoobies could be subject to a fine. He said Scoobies is instituting several safeguards to prevent a similar problem, including posting a staff member at the door, taking a head count every 30 minutes and hiring an additional employee to ensure an 8-to-1 ratio of supervision for the 37 children.

Also, persons authorized to pick up children will be given identification badges to show when they sign out youngsters and will have to accompany the children, not walk out ahead of them.