3 children, 2 adults dead after school bus and semitruck collide in Illinois: Police

Three children and two adults died after a school bus collided with a semitruck on U.S. Route 24 in Illinois on Monday, authorities said.

The fatal collision between the school bus and the semitruck carrying sand happened on the highway at 11:30 a.m., local time, in Rushville, Illinois State Police said during a press briefing.

Preliminary reports indicate the bus was heading East on Route 24 and for an "unknown reason," crossed over into the Westbound lanes in front of the semi-truck, police said.

Both vehicles erupted into flames after the collision, according to authorities.

The school bus was transporting three children at the time of the crash. The three children, as well as both drivers, were pronounced dead at the scene, authorities said.

The children who died in the accident were preschoolers, Schuyler County Coroner Terry Millslagle told ABC News. All of the families of the victims have been contacted.

Later on Monday, Schuyler County coroner confirmed the deaths of the two adults, David Coufal, 72 and Angela Spiker, 57, as well as the the deaths of the three children, Maria Miller, 5, Andrew Miller, 3 and Noah Driscoll, 3.

Schuyler-Industry Schools confirmed the incident with a "heavy heart" in a Facebook post on Monday .

"It is with a heavy heart that we announce our school community has lost both staff and students in the traffic incident involving one of our school buses this morning," the post read. "Our thoughts and prayers go out to the families and our community."

The school district canceled school on Tuesday and Wednesday, following the incident.

The National Transportation Safety Board said it will investigate.

"The NTSB, in coordination with Illinois State Police, is sending a team to conduct a safety investigation into Monday’s multivehicle collision involving a school bus and a truck tractor in combination with a semitrailer on U.S. Highway 24 in Rushville, Schuyler County, Illinois," read a post on the NTSB X page.

-- ABC News' Darren Reynolds and Jianna E. Cousin contributed to this report.