ETNA, Ohio (AP) — A charter bus carrying students from Tuscarawas Valley High School was rear-ended by a semi-truck on an Ohio highway Tuesday morning, leaving three people dead and 15 others injured, according to an emergency official.

The charter bus was transporting students from the Tuscarawas Valley Local School District in eastern Ohio, Licking County Emergency Management Agency Director Sean Grady said. There were a total of 57 people onboard, he said.

The bus was carrying Tuscarawas Valley students and chaperones to an Ohio School Boards Association conference in Columbus, Superintendent Derek Varansky said.

The conference was canceled after organizers learned of the crash.