One person was killed and dozens injured early Wednesday after the driver of a charter bus with nearly 50 people on board veered off a highway then overcorrected, causing the bus to land on its side, the Texas Department of Public Safety said.

After the bus overturned on U.S. 59 near Victoria, a small pickup truck rammed into it, DPS spokesman Tom Vinger said. The driver of the truck was uninjured. The bus left Monterrey, Mexico, about 7:30 p.m. Tuesday and was headed to Houston when it crashed about 4:15 a.m., Vinger said.

"The investigation is centering on driver fatigue," Vinger said. "It looks like he ran off the road, overcorrected then tipped over on the passenger side."

The bus was operated by Capricorn Bus Lines Inc. in Houston. Francisca Flores, manager of the bus company her family owns, said this is the first wreck in the nine years since Capricorn began. She said 46 people were on the bus declined further comment on the wreck because she was still waiting for information.

The company has four buses and only makes trips between Houston and Monterrey, she said.

The identity of the man who was killed on the bus wasn't immediately released, nor was the name of the bus driver. Vinger said the driver wasn't seriously injured, and that it's too early to tell whether he'll face charges.

Vinger didn't know whether there was more than one driver. He also said weather was not a factor in the wreck.

DeTar Healthcare System in Victoria took 22 of the passengers, said spokeswoman Judith Barefield. Of those, one was in critical condition, one was transferred to another hospital outside Victoria for a "higher level of treatment," two were in serious condition, 11 were in fair condition and seven were treated and released, she said.

Another 24 people were brought to Citizens Medical Center in Victoria, said spokeswoman Shannon Spree. Of those, one was airlifted to Brooke Army Medical Center in San Antonio and two were airlifted to Wilford Hall Medical Center in San Antonio, she said. One of those airlifted had a severe head injury, she said.

Nine others were admitted to Citizens Medical Center, two in intensive care. The other 12 were treated and released or being treated, Spree said. She said three or four of the passengers had broken backs and that a lot of them had orthopedic injuries such as broken collar bones and arm injuries.

San Antonio's University Hospital had received one minor patient in critical condition, said spokeswoman Dora Quiroga.

Wilford Hall Medical Center spokeswoman Sue Campbell confirmed that two patients were transported there. She said they were in surgery and their conditions were unknown.

A message left for Brooke Army Medical Center was not immediately returned Wednesday.

Victoria is about 125 miles southwest of Houston and 110 miles southeast of San Antonio.