An upcoming YMCA summer camp session in Idaho has been canceled so staffers can deal with the emotional trauma of a bus crash that injured almost a dozen people, an official said Saturday, as police still tried to determine the cause.

The bus was carrying about 30 adolescent campers and staff back to Boise from the Treasure Valley YMCA’s camp at Horsethief Reservoir. Eleven passengers were hospitalized, seven in critical condition, after the bus rolled over on a winding Idaho highway north of the town of Banks on Friday afternoon, Idaho State Police said. The flipped bus blocked a state highway that follows the Payette River, causing a massive traffic jam.

The four-day camp at Horsethief Reservoir planned to start Sunday won’t be held, said Treasure Valley YMCA President and CEO David Duro. He said it “would be unfair” to ask the camp counselors, who had spent days with the youths who were injured, to operate as usual.

“It’s like a family member is in a traumatic event,” Duro said Saturday. “It’s easy for your mind to wander and for you just to be concerned about them and maybe not provide the magic that YMCA camp deserves.”

At the YMCA camp, youngsters can engage in canoeing, archery, zip-lining and other outdoor activities. The popular camp runs multiple sessions throughout the summer for kids between second and 11th grades.

St. Luke’s Health System was caring for multiple patients injured in the crash at its Boise and Meridian hospitals, a public relations coordinator said Friday. A hospital spokesperson on Saturday declined to provide any update on the patients’ conditions and referred questions to the Idaho State Police.

The crash is being investigated as a single-vehicle collision, Aaron Snell, a spokesperson for the state police, said Saturday. He said rumors that a truck contributed to the crash were false. As is routine, investigators will see whether alcohol or drugs were a factor, Snell said.

The driver was treated and released from the hospital, Duro said. The Y had contracted with Caldwell Transportation for the bus service. Calls to the company’s offices in Boise went unanswered Saturday.

The crash blocked both lanes of Highway 55 for hours on Friday. The two-lane road is one of the state’s two major north-south routes, and it is frequently packed with weekend travelers headed from the Boise region to vacation destinations or popular campsites.