(CNN) -- Four people died when a school bus collided with a tractor-trailer at an intersection in Nebraska's rural Webster County on Wednesday, the sheriff's department said. Both drivers were both killed as well as two passengers on the bus, Webster County Sheriff Troy R. Schmitz said. The sheriff's department did not immediately say whether any of the victims were children. The accident occurred at the intersection of County Road 1800 and Country Road R outside the town of Blue Hill, near the Nebraska-Kansas state line, Schmitz told CNN affiliate KHGI. The accident occurred between 4:30 p.m. and 4:45 p.m. local time, he said. Schmitz declined to release details about the accident, citing a pending investigation. How safe are school buses?
A school bus and a tractor-trailer collided near Blue Hill, Nebraska, the sheriff says . Both drivers have been killed, he says . Also killed were two passengers on the school bus, he says .