UVALDE, Texas -

At least 21 people were reportedly injured when a school bus rolled over near Uvalde Thursday afternoon.

Two of the students and an adult sponsor were flown to University Hospital in San Antonio. There was no word on the extent of their injuries.

The other 16 students, another sponsor and the driver suffered minor injuries and were treated at Uvalde Memorial Hospital, officials said.

The students on board attend Lyndon B. Johnson High School in Laredo. They were headed to a UIL criminal justice competition in Uvalde when the accident happened.

The cause of the crash remained under investigation Thursday evening.