CNN — Two people are dead, including a child, after a concrete truck struck a school bus full of pre-K children returning from a field trip head-on in Bastrop County, Texas, according to officials.

The bus, traveling westbound on State Highway 21, was hit by the concrete truck traveling in the other direction, according to Texas Department of Public Safety Sgt. Deon Cockrell. One child on the bus and an adult passenger in a vehicle behind the bus died.

In an updated post on X, Austin-Travis County EMS said a total of 53 patients were evaluated at the scene. Four patients were taken to hospitals in critical condition and six in potentially serious condition. The rest sustained minor injuries and were either taken to hospitals or to the unification center, the post said.

It is still early in the investigation, but it does not appear the truck driver was under the influence, Cockrell added.

In a statement, Hays Consolidated Independent School district said 44 pre-K students and 11 adults from Tom Green Elementary were returning from a field trip to the Bastrop Zoo when the crash took place.

School staff, administrators, counselors, safety and security personnel went to the scene, the district added.

School superintendent Eric Wright wrote he was “heartbroken” by the death of “a precious young boy” in a letter to the school community.

“There are no words that can express my sorrow for the student’s family, the Tom Green Elementary School family, and our greater Hays CISD community,” Wright wrote. “I am also saddened to learn of the death of a person who was driving a car that was on the road behind our bus.”

The superintendent commended the teachers and school staff for their work during the “unspeakable event,” as well as the bus driver, who he said “insisted that medical personnel tend to the children first” even though she herself was injured.

He added the school’s reunification process was completed at 6:45 p.m. local time.

CNN has reached out to officials for additional information.

CNN’s Raja Razek and Sarah Engel contributed to this report.