HOUSTON (AP) — A chartered bus coming from Mexico veered off a highway early Wednesday and overturned, killing one passenger and injuring dozens of others, at least six of them critically, authorities said.

Some of the passengers crawled out an emergency exit on the roof.

The bus had left Monterrey, Mexico, on Tuesday evening and was headed to Houston when it crashed several hours before dawn south of Victoria, about 125 miles southwest of Houston, authorities said.

"The investigation is centering on driver fatigue," said Tom Vinger, spokesman for the Texas Department of Public Safety.