Last Updated 1:45 p.m. ET
IRVING, Texas A chartered bus overturned on a highway just east of Dallas-Fort Worth International Airport, killing two passengers, reports CBS Station KTVT.
The Cardinal Coach Line bus was traveling along President George Bush Turnpike, near Belt Line Road in Irving, when the bus suddenly weaved across the highway, stuck a concrete barrier and toppled over shortly after 9:00 a.m., witnesses said.
More than 30 people were injured.
"We ended up swirling and weaving and then ended up on the side," passenger Daniel Risik, 73, told The Dallas Morning News. "People were screaming and hollering, a very traumatic situation to say the least."
He said most people aboard the bus, which picked up passengers in Fort Worth, weren't wearing seat belts.
"People were piled on top of each other," he said. "It was unbelievable. A lady had pinned me. Rescue got there and started pulling people out of a roof emergency hatch. People were hollering, screaming, there was blood all over the place. It was unbelievable."
The cause of the accident was not immediately clear.
The bus, which was carrying about 45 people, was headed to a casino in Oklahoma, officials said.
State Trooper Kyle Bradford told KTVT one person pinned in the wreckage was removed; Trooper Bradford was still trying to confirm the condition of that individual.
Emergency workers used emergency exits on top of the bus to pull passengers from within the vehicle.
KTVT reports two passengers died, according to officials on the scene.
Fifteen victims, including the driver of the bus, were taken to Parkland Hospital in Dallas, most by air ambulance. A spokeswoman for Baylor Medical Center in Irving said 13 patients arrived at the hospital following the accident. Officials at Las Colinas Medical Center in Irving confirmed six patients were there, though details were not immediately available on their conditions.
Traffic in both directions along the toll road was shut down while crews continue their work at the scene.
The bus belongs to Cardinal Coach Line based in Mansfield, just south of the Dallas area. The company has experienced no crashes within the past two years and has earned 'satisfactory' safety rating. They have been in business since March 2007.
Authorities from the Texas Department of Public Safety, the Irving Police Department and Dallas Area Rapid Transit are working on the scene, with the Texas DPS taking charge in the investigation.
National Transportation Safety Board spokeswoman Kelly Nantel said the agency is sending investigators to Irving.