A 4-year-old pupil with special needs was discovered on a city-operated bus in the District on Tuesday afternoon, long after he should have been dropped off at school, officials said.

The boy appeared to be in good health after spending more than six hours on the bus, according to the Office of the State Superintendent of Education, which is responsible for transporting special-needs students in the District.

A spokesman for the office said in a statement that the agency was “troubled to learn” about the incident and is investigating.

The boy was picked up from his home at 7:35 a.m. and the bus went to his school, the office said, but “it is unclear why he did not get off.”

The bus returned to its Southwest terminal at 8:52 a.m. The driver and an attendant got off the bus, but did not notice the child, who apparently had fallen asleep, the OSSE statement said.

The agency’s transportation department learned at about 2:05 p.m. that the student had been left on the bus, which was at the terminal, the statement said.

According to the statement, the student was found in his booster seat on the bus by the driver and attendant, who went to the vehicle to inspect it before going on their afternoon runs.

The boy was awake and alert and was not crying, the OSSE said. The student’s mother was called, along with the head of the transportation unit and paramedics.

The boy was examined and cleared for release to his mother, the statement said.

OSSE said it transports about 3,100 students on more than 600 buses.

The statement said that based on its initial investigation, “two employees were separated from the agency.”