The CEO of Community Action Program of Lancaster County pledged to conduct a vigorous investigation after a 4-year-old girl was left on a bus Friday morning.

"I'm extremely upset about it," Mark Esterbrook said Saturday. "It's an unacceptable standard of care for children."

The bus driver has been suspended pending conclusion of the investigation, he said.

According to Esterbrook, the child was enrolled in the Head Start program. She was riding a CAP bus, and when the vehicle stopped at the Head Start drop-off center in Lancaster city at about 8:30 a.m., the girl got out, he said.

But as the driver was distracted by a second child, Esterbrook said, the 4-year-old climbed back on the bus.

The driver then parked the bus around the corner, locked it and left, he said. At around 10 a.m., the driver returned to the vehicle and began filling out paperwork, Esterbrook said.

Twenty minutes or so into that task, the driver noticed the girl sitting quietly on the bus.

Stunned, the driver immediately drove the child home to her mother and explained what happened, Esterbrook said.

Several CAP officials have called the mother to apologize, he said.

The agency expects to have its investigation concluded by the middle of the week, Esterbrook said.

"We will take appropriate personnel action," he said.

Contact Paula Wolf, Sunday News staff writer, at pwolf@lnpnews.com.