At least 13 people were killed and more than 40 injured - some seriously - Friday when a chartered bus carrying Vietnamese churchgoers plunged off a highway bridge in the US state of Texas.

The accident occurred around 12:45 am (0545 GMT) when the bus carrying 55 church members from Houston, Texas to a fair in the state of Missouri crashed around 100 kilometres north of Dallas, police said.

All of the passengers were believed to be Vietnamese, part of large congregations from the Houston's Vietnamese Martyrs Church and Our Lady of Lavang Church that were travelling to the Missouri fair.

The crash may have been caused by a blown tyre, local media reported, though police officials said it would take some time to "reconstruct" the accident.

At least 18 helicopters and a number of ambulances were used to transfer the injured to local hospitals and recover the dead, the Dallas Morning News reported.

But the rescue was hampered by the fact that nearly all the passengers did not speak English, said police, who described a horrific scene as the bus lay on its side at the bottom of the bridge.

"Youve got 50-something people laying everywhere," officer Tony Walden told the paper. I don't even know how to describe it."