The incident happened at Bamaur More under Shivsagar police station on National Highway - 2, popularly known as Grand Trunk Road, police said.
The deceased have been identified as Puja Kumari (10) and Mamata Kumari (11). The injured girl Sheetla Kumari (11) has been admitted to Sadar Hospital, where her condition is stated to be serious, Sasaram Sadar Sub-divisional Officer (SDO) Nalin Kumar said.
"The schoolgirls were going to Shivsagar to attend classes. They were waiting for their school bus to arrive, when a speeding truck, overloaded with sand lost its control and ran over them. Two girls died on the spot. Both of them were residents of Bamaur village," Kumar added.
The SDO said Rs 2 lakh each will be given to the kin of the two dead girls.
Meanwhile, irate villagers of the area blocked the busy NH-2 for a couple of hours soon after the incident. They lifted the blockade after administrative officials assured them of strict action against the culprits.