MCKINNEY, Texas -- Police are investigating what caused a young woman to drive erratically before crashing into a school bus full of students late Thursday night, killing her instantly.

Officers were called about an erratic Jeep Wrangler at about 11:30 p.m. As police looked for the vehicle, they were called about a crash involving a Denton ISD school bus near West University Drive and Wisteria Way.

The driver of the Jeep, described as a young female, was pronounced dead at the scene.

Students on the bus were coming back from a tennis tournament. The bus driver and students weren't injured.

It took police about three hours to remove the Jeep from under the school bus.

The driver hasn't been identified.