BERLIN - An eight-year-old boy was inadvertently locked inside a school bus for more than 12 hours on a steamy hot day in the eastern German town of Cottbus after the driver forgot about him, German daily Bild reported on Friday.

The boy got on the bus at his home in the morning but did not show up for school. After dropping the children off, the bus driver returned to the bus company's transport lot but did not notice that the one young passenger was still on board.

"The bus was parked far away and wasn't very visible from the office," police spokesperson Torsten Wendt was quoted saying. It was only when his mother anxiously called the authorities that boy's disappearance was noticed.

After hours of searching, the boy was found on the bus later that night in reasonably good spirits even though the temperature had climbed to 30 degrees Celsius.

He was found lying shirt-less on the floor under the seats. He even rationed his school-lunch so that it might last all night.

"The bus driver forgot me," the boy told police, according to Bild. It was not immediately clear why he did not speak out before the driver left the bus. Police are investigating whether to charge the driver with negligence.