The crash, details of which were not immediately provided, occurred shortly before 9 a.m. local time on Interstate-70 near Etna Township, about 34km east of Columbus, the Ohio state capital, according to the Ohio State Highway Patrol.

Local news media footage from the scene showed a large motor coach that appeared to have been struck from behind by a big-rig truck, the scorched wreckage of which was all that remained intact. A damaged sport utility vehicle was also visible beside the truck.

Highway Patrol lieutenant Nate Dennis said a total of five vehicles were involved in the crash, and that 18 people from the bus were transported to area hospitals.

John Wieber, a spokesman for the Licking County Emergency Management Agency, said six fatalities had been confirmed. But it was not made clear how many were from the bus or whether any were among the victims who had been taken to hospitals.

The identities of the dead were not immediately made public. The cause of the crash was under investigation. From news footage of the crash scene, the skies were clear and it did not appear that weather was a factor.

The chartered bus was carrying a group of high school students and their adult chaperones from the Tuscarawas Valley school system in eastern Ohio to a conference of the Ohio School Boards in Columbus. The event was postponed for the day following the crash.

Ohio governor Mike DeWine ordered flags to be flown at half-staff in Licking County and at the Ohio Statehouse.