Updated

One of two buses taking Missouri sixth-graders to an annual campout overturned in northeast Kansas on Wednesday, injuring at least 20 of those onboard, including the driver.

The bus, which was carrying sixth-grade girls from Pembroke Hills School, overturned while rounding a sharp curve on a highway ramp in Bonner Springs, about 20 miles west of Kansas City, Mo., where the private school is located, said Kansas Highway Patrol Trooper Howard Dickinson. Their male classmates were on the other bus.

None of the injuries were life-threatening, but 20 of the 36 people onboard, including the driver, were taken to hospitals. Some had just bruises but others had head and neck injuries, Dickinson said.

"The hardest thing at first was getting the girls calmed down and squared away," he said.

Several of the girls were placed on backboards as a precaution, Dickinson said. He said the driver initially was up and helping the students after the crash but eventually lied down. Investigators hadn't interviewed the driver yet, he said.

At least two good Samaritans helped remove students from the bus, which had toppled onto its right side and blocked the main door.

Roger Twitchel, who manages a body shop next to the crash site, said he went over to help after the bus overturned.

"For the most part, most of the girls were acting pretty brave and were up and walking and talking."

He said the injuries ranged from as little as a cut lip to possible broken bones. He said emergency crews arrived quickly.

"For the most part, it was a bunch of brave little 11-year-old girls. Some were comforting each other."

Dr. Denise Dowd, an emergency room doctor at Children's Mercy Hospital in Kansas City, Mo., said the injuries that the hospital treated were minor.

"Good news so far. We received four patients, all with minor bumps and bruises, and it looks like they're doing OK at this point. Nothing major."

The children who weren't seriously hurt were taken to Bonner Springs High School to be picked up by their parents.

Beth Bryant, a Pembroke Hills spokeswoman, said the children were headed to Tall Oaks camp in Linwood, Kan., for the school's annual campout to mark the start of the school year.

Tow trucks were able to get the bus back on its wheels about two hours after the crash

Warrenville, Ill.-based Durham School Services, which operates the bus, deferred questions to the company's public relations firm, which by mid-afternoon hadn't returned multiple messages seeking comment.