Two people, including a child, were killed, and several more injured, when a school bus carrying more than three dozen pre-K students Friday afternoon was involved in a crash on a highway in Bastrop County, Texas, east of Austin, state officials said.

The school bus was traveling west on Highway 21 at about 2 p.m. local time when a concrete truck "veered into the school bus's lane and struck the school bus," Sgt. Deon Cockrell with the Texas Department of Public Safety said in a news briefing Friday evening.

A boy riding on the bus was killed in the crash, Cockrell said, along with a man who was in a third vehicle that was traveling behind the school bus. The names of the deceased victims were not immediately provided.

The Hays Consolidated Independent School District confirmed in a statement that the school bus was carrying pre-K students from Tom Green Elementary School returning from a field trip to the Bastrop Zoo when the crash occurred.

The bus was carrying 44 students and 11 adults at the time of the crash, the district said.

A total of 53 patients were evaluated at the crash scene, Kevin Parker, division chief for Austin-Travis County Emergency Medical Services, told reporters.

In addition to the two people killed, four patients were airlifted to area hospitals with critical injuries, and six more were taken to hospitals by ground ambulance, Parker disclosed.

The remainder had minor injuries and were either treated at the scene or transported to a hospital, Parker said.

"We did an on-scene triage and continuous triage as we were getting units available to move those victims," Parker said.

Cockrell wouldn't speculate on what exactly caused the crash or whether charges would be filed, only saying that it was under investigation. 

"I am shocked and deeply saddened to hear about the school bus accident in Bastrop County today," Sen. John Cornyn of Texas wrote in a social media post. "Please join me in praying for these children, educators, and their families, especially those who have lost loved ones, during this difficult time."

In:
• Austin
• School Bus
• School Bus Accident
• Texas
• Bus Crash

Faris Tanyos

Faris Tanyos is a news editor for CBSNews.com, where he writes and edits stories and tracks breaking news. He previously worked as a digital news producer at several local news stations up and down the West Coast.