A bus fire that killed 11 young children and two adults in Shandong province last month is thought to have been started by the driver, who was among the dead, police said on Friday in Weihai, Shandong province.

The bus driver, Cong Weizi, is suspected of starting the fire to vent his anger over his overtime and night shift subsidies being suspended, Wang Jincheng, deputy head of the Shandong Provincial Public Security Bureau, said at a news conference on Friday in Weihai.

Cong is thought to have bought gasoline from a gas station and set it on fire in the bus, Wang said.