SEATTLE — A truck driver who may have been fatigued veered into oncoming traffic on a rural Washington state highway Thursday, killing a woman driving a car and crashing into a school bus loaded with children, a state trooper said.

Fifty-six people, most of them children, were taken to the hospital after the morning collision on Highway 97 north of Orondo, a community along the banks of the Columbia River about 150 miles east of Seattle, officials said.

A woman driving a passenger car, who has not been publicly identified, was pronounced dead at the scene, state troopers said. Seven other people, including the truck driver and a truck passenger, were badly injured and transported by ambulance, Douglas County Fire said.

Trooper Darren Wright of the Washington State Patrol said it appeared that the box truck driver, who was traveling south, was falling asleep before his truck crossed into oncoming traffic, striking the car and bus, both traveling north.

“The early investigation indicates fatigue on the part of the truck driver,” he said.

Wright said the school bus driver and two occupants of the truck were also taken to the hospital. The truck occupants were reported in serious condition. The extent of the school bus driver’s injuries was not immediately known.

The school bus had been carrying 40 to 50 students of all ages from the Orondo School District, school board member Jennifer Foreman said.

“None of the kids on the bus were critically injured,” she said.

All the children were taken to Central Washington Hospital as a precaution and were being reunited with their parents at the facility, she said.

Photographs from the scene posted online showed that the front ends of both the bus and truck were badly smashed.