Nyhart said investigators were struggling to identify the injured and were not certain how many people were on the 24-passenger bus or how many had been transported to hospitals in Kingman and Las Vegas.
The bus was traveling north on U.S. 93 when it veered left and then right across the median, Nyhart said. It rolled at least once before stopping.
He believes all but one of the victims killed at the scene had been ejected from the bus.
Nyhart said five people had suffered life-threatening injuries. "We're hopeful that those people can be stabilized and at least the death toll stop where it is," he said.
The driver of the bus was among those in critical condition, he said.
The tourists on the bus were Chinese nationals who had flown from Shanghai to San Francisco and had most recently been in Las Vegas, according to DPS.
The group left Las Vegas early Friday for a trip to the Grand Canyon and was returning when the crash occurred around 4 p.m.
Several people rushed to the scene from a nearby diner immediately afterward.
Sheila Larsen, who works at Rosie's Den, said she went outside after hearing a loud crash and screams and found people lying on the roadway, with paper and money strewn across the area.
She said the best she could do to comfort the victims was bring them blankets, towels and water. "The woman I was trying to comfort didn't speak English. I was trying to comfort her and she died," Larsen said.
Debbie Diamond, who also works at Rosie's Den, said she's seen many accidents on the highway, the main route between Phoenix and Las Vegas, but never one like that.
"I just keep praying, that's all you can do in a situation like this," she said.
