RUSHVILLE, Ill. (AP) — Authorities have identified the five people killed in a fiery collision between a school bus and semitruck on a highway in rural Illinois, including a young brother and sister, another 3-year-old boy and both drivers.

The eastbound bus from Schuyler-Industry Schools crossed into westbound U.S. Route 24 “for an unknown reason” Monday and into the path of a semi carrying sand, according to the state police’s preliminary findings.

Both vehicles “became engulfed in flames” after colliding, which happened at around 11:30 a.m. in Rushville, a Schuyler County community of about 3,000 roughly 60 miles (95 kilometers) west of Springfield, the agency said. All four people aboard the bus — three children and the driver — were killed, as was the truck’s driver.

The county coroner identified the children as 5-year-old Maria Miller, 3-year-old Andrew Miller and 3-year-old Noah Driscoll, all from Rushville, state police said. Maria and Andrew Miller were sister and brother, the county coroner confirmed Tuesday.

The bus driver was identified as Angela Spiker, 57, of Rushville, and the truck driver as David Coufal, 72, who was from the nearby village of Browning.

Sheriff Bill Redshaw said that at the time of the crash, the bus was taking the kids to school.

He told reporters Monday that the tragedy hit the small community hard.

“There’s not really words at this time that can be said,” Redshaw said. “When you have a loss of life like this, it’s devastating.”

Schuyler-Industry Schools canceled classes Tuesday and Wednesday because of the crash.

“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 school district said in a statement.

The cause of the crash is under investigation by a National Transportation Safety Board team and the state police, the Illinois agency announced.

The coroner said autopsies on the victims were being conducted Tuesday in Springfield.