Palestinian authorities said a grave site discovered at the Nasser hospital, the main medical facility in central Gaza, contained nearly 400 bodies
The school bus was hit by a speeding truck on the Patiali road.
The accident was a result of fog, an official told IANS.
While schools in the state have been closed until Jan 20 due to poor weather conditions, the JS Public school, to which the bus belonged, was open.
The bus was carrying more than 60 students at the time of the accident.