(NEW YORK) — Six people were killed in a multi-vehicle crash on an Ohio highway Tuesday morning, officials said.

Five vehicles — including a charter bus carrying Ohio high school students — were involved in the crash, which occurred on Interstate 70 in Etna shortly before 9 a.m. local time, officials said.

More details on the crash were not immediately available. Sean Grady, the director of emergency management for Licking County, told ABC News the Ohio State Highway Patrol will provide more information on the incident, including the fatalities.

A Pioneer Trails charter bus transporting students from Tuscarawas Valley School was among the five vehicles involved in the crash, according to Ohio Gov. Mike DeWine.

“Let me just say that this is our worst nightmare when we have a bus full of children in a crash,” DeWine said during a press briefing Tuesday.

Gov. DeWine, earlier Tuesday, confirmed the crash was fatal but said no other details would be released until all the proper notifications have been made. Eighteen people were transported to seven area hospitals, he said.

Tuscarawas Valley Local Schools superintendent Derek Varansky said students and chaperones were traveling to the Ohio School Boards Association conference in Columbus when their charter bus 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 said in a message to the school community.

In addition to high school students, parents and teachers were among those on board, according to the Ohio State Highway Patrol’s Tuscarawas office.

Pioneer Trails said it is “fully cooperating with the authorities as we work to find the cause of the accident.”

“Our thoughts and prayers go out to all of those impacted by this accident,” the company said in a statement. “As this is an ongoing investigation, there will be no further comments.”

The National Transportation Safety Board said it was sending a team of investigators to the crash site. NTSB chair Jennifer Homendy and the team were expected to arrive Tuesday evening, the agency said.

ABC News’ Alexandra Faul and Sam Sweeney contributed to this report.

This is a developing story. Please check back for updates.

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