Five people, including three children, were killed on Monday morning when a school bus collided with a semi-truck on an Illinois roadway, setting both vehicles ablaze, the police said.

The crash happened about 11:30 a.m. on Route 24 near Rushville, a city of about 2,600 residents in western Illinois roughly 50 miles northwest of Springfield. The school bus, which was carrying three children, was traveling west when it crossed into the eastbound lane and struck a semi-truck carrying sand, Capt. Jody Huffman of the Illinois State Police said at a news conference.

The impact sparked a fire that engulfed both vehicles, Captain Huffman said, noting that all five people in the vehicles were killed. The driver of each vehicle and the three children were pronounced dead at the scene. Officials said they were still investigating the crash and were trying to determine why the school bus had veered into oncoming traffic.

Officials did not immediately release the ages or identities of the victims, or what school the children attended. But Terry L. Millsagle, the Schuyler county coroner, said at the news conference that he had contacted their families.

“Out of respect for everyone involved, no names or further information will be released at this time,” the school district said in a statement. “School will not be in session tomorrow, Tuesday, March 12 and Wednesday, March 13.”

The school bus belonged to the Schuyler-Industry Schools district, which is based in Rushville.

The bodies were set to be transported to Springfield Memorial Hospital for a post-examination, Mr. Millsagle added.