New Delhi, India (CNN) A speeding van rammed into a middle school in eastern India on Saturday, killing nine children, authorities said.

In addition to the fatalities, 10 others were critically injured in the incident at the school in Muzzafarpur, in Bihar state, said Vivek Kumar, a local police superintendent.

The students were in school Saturday, the police official said.

"The incident happened when the school had just finished and the students had gathered outside the school building," Kumar said.

Police arrested the driver and an investigation is ongoing.