ETNA, Ohio (NewsNation) — At least three people were killed and 15 others injured Tuesday after a charter bus carrying students from a high school was rear-ended by a semi-truck on an Ohio highway, according to an emergency official.

The charter bus was transporting students and chaperones from Tuscarawas Valley High School, in Tuscarawas County, Licking County Emergency Management Agency Director Sean Grady confirmed to NewsNation. There were a total of 57 people onboard.

The accident occurred shortly before 9 a.m. on Interstate 70 West in Licking County, near the Smoke Road underpass. The cause was not immediately known. The injured are being treated at five area hospitals.

Those aboard the charter bus were en route to the Ohio School Boards Association Conference in Columbus, the Tuscarawas Valley School District said in a statement.

“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. Our Trojan family is strong, and it will take that strength and love to get throughout these coming challenging days,” said Tuscarawas Valley School District Superintendent Dr. Derek Varansky.

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The American Red Cross of Central and Southern Ohio said it fulfilled a request for more blood from one hospital in the area, sending 30 units to a hospital in the Mount Carmel Health System, said Marita Salkowski, regional communications director.

A center was set up at a United Methodist Church in Etna for bus passengers not in need of medical attention to go to and contact loved ones, she said.

Numerous emergency responders were at the scene, and Ohio Department of Transportation cameras from the area showed smoke coming from the crash site. The highway was closed in both directions and numerous traffic delays were reported.

At 10:30 a.m., two school buses were seen arriving at the scene, escorted by police. Several dozen people boarded the buses, which drove away about 20 minutes later, NewsNation affiliate WCMH reports.

Mickey Lymon, an investigator with the Licking County Coroner’s Office, said they had been called to the scene, but deferred other questions to the state police.