(NewsNation) — The National Transportation Safety Board detailed its upcoming investigation into Tuesday’s deadly multivehicle crash on an Ohio highway that killed six and injured another 18.

On Tuesday, a charter bus carrying students and chaperones from Tuscarawas Valley High School in Tuscarawas County was rear-ended by a semitrailer on Interstate 70 West in Licking County.

The NTSB says five vehicles were involved in the crash: the motorcoach, an SUV traveling with the motorcoach, another red SUV and two commercial vehicles. It is currently unclear what series of events led to the crash.

The investigation is expected to take 12 to 18 months, but important updates will be provided periodically, NTSB Chair Jennifer Homendy said in a press conference.

Homendy says the NTSB will have 16 investigators and two family assistance personnel in the investigation along with support from experts across multiple agencies.

Before the comprehensive crash report is released, the NTSB will “provide entities with safety deficiencies” that can be addressed as soon as they are identified, Homendy said.

She added that the “implementation” of any recommendations that come out of that will be key in preventing future crashes.

“We have a public health crisis on our roads,” Homendy said in the press conference. “We need all hands on deck.”

Three of the passengers on the bus were pronounced dead on the scene. They have been identified as John W. Mosely, 18; Jeffery D. Worrell, 18; and Katelyn N. Owens, 15.

The bus driver and 15 students were transported to a local hospital.

Those aboard the charter bus were on their way to the Ohio School Boards Association Conference, the Tuscarawas Valley School District said in a statement.

The other three people who died were in a passenger vehicle and were also declared dead on the scene. They are Dave Kennat, 56; Kristy Gaynor, 39; and Shannon Wigfield, 45.