ETNA, Ohio – Three people are dead and 15 others injured after a charter bus carrying high school students and a semi-truck crashed on a highway in Ohio.

Tuscarawas Valley Local Schools, an Ohio school district in Zoarville, said late Tuesday morning that the bus was carrying students and chaperones, and that there may have been "serious injuries" among those on board.

Ohio State Highway Patrol Lt. Nate Dennis said the crash involved five vehicles, and 18 people were taken from the bus.

Around 8:45 a.m. Tuesday, dozens of emergency personnel from across Licking County and eastern Franklin County were dispatched to the area on a report of a crash.

Derek Varansky, superintendent for Tuscarawas Valley, said on Facebook that "a charter bus carrying Tusky Valley students and chaperones on the way to the Ohio School Boards Association conference in Columbus was involved in a very serious accident."

"We understand from law enforcement that there may be multiple serious injuries and we are working to learn the details," Varansky wrote. "Right now, our focus is on getting in touch with our Tusky Valley families who had loved ones on the bus and providing support to our entire school community."

'Sick to my stomach': Tuscarawas Valley school students, chaperones on bus

A steady stream of vehicles pulled into the Tuscarawas Valley Middle-High School parking lot Tuesday morning, as parents came to pick up their grief-stricken children. Staff members came to the vehicles, conferred with the drivers and then went back into the school to retrieve their children.

"I'm sick. I'm sick to my stomach," parent Laurie Fragasse said when she picked up her daughter Camrynn just before noon.

Camrynn, an eighth grader, said she was scared and sad.

"I don't really know how to feel right now," she said.

Governor of Ohio: 'This is our worst nightmare'

During a Tuesday news conference at a rest stop, Ohio Gov. Mike DeWine said his prayers go out to all involved in the crash and their families.

“This is our worst nightmare when we have a bus full of children involved in a crash and certainly the worst nightmare families can endure or a school can endure," DeWine said.

Conference canceled in light of tragedy

The students were headed to the the Ohio School Board Association annual convention held in Columbus. The event, which was held from Nov. 12 through 14, features speakers, a trade show and a student success exposition, according to the OSBA website. The remainder of the event was cancelled Tuesday, an OSBA spokesperson said.

"Given this devastating news, we have canceled our conference," an OSBA statement read. "Right now, our focus is on providing support to Tuscarawas Valley. That includes making grief counselors from our trade show available."

Tusky Valley families begin gathering at Etna relief site

By 2 p.m., almost all of the students not transported to the hospital had been reunified with their students at the Etna United Methodist Church. In total, 34 students were taken there after the crash, said Don Hawkins, regional communications manager for the Red Cross of Central and Southern Ohio, which Licking County Emergency Management contacted for help.

“Whenever something like this happens, we work with local EMA to assist them. We don’t try to take over the operation,” Hawkins said.

Mount Carmel East hospital also requested and received 30 extra units of blood, he added.

“It’s heavy; it’s really heavy. It really hurts to see this happen to anyone, to kids … especially at the holiday season,” Hawkins said. “Families are going to be devastated. Our hearts go out to them. Three families are going to feel that forever. It hurts.”

Bus company cooperating with investigators in mass casualty incident

The bus involved in the crash is from Pioneer Trails, a family-owned bus business based in Millersburg, Ohio. In a statement on Facebook, Pioneer Trails "is fully cooperating with the authorities as we work to find the cause of the accident" and sends prayers to the victims and their families.

According to U.S. Department of Transportation inspections, the company has had one other crash involving an injury in the past 24 months. The company received a satisfactory rating, meaning records indicate no evidence of substantial noncompliance with safety requirements.

Dispatchers classified the crash as a "mass casualty incident, level 3," which indicates 10 or more people may have been injured and there was a need for paramedics, fire crews and hospital readiness across the region. Casualty does not necessarily mean fatalities in the way it is used by dispatchers.

Contributing: The Associated Press; USA TODAY Network Ohio reporters Maria DeVito, Pam James and Nancy Molnar