NEW DELHI — Thirteen children were killed after their school bus was hit by a train in northern India on Thursday. The accident’s cause may have been infuriatingly simple: The bus driver was wearing earphones.

The authorities said the driver had not seen or heard the enormous train barreling toward him, blowing its horn. As the bus crossed the railroad tracks, he had earphones in his ears, witnesses said, and he was listening to loud music.

“The children were crying out for the driver to stop,’’ said R. C. Srivastava, a senior railways official.

It was the third known accident in recent years in which a school bus driver in India who was wearing earphones did not hear a train coming, resulting in the deaths of children.