Irving, TX (CNN) — UPDATE (4:35pm) - CNN - Two people were dead and dozens of others were taken to hospitals after a charter bus bound for Oklahoma casinos overturned on a Dallas-area turnpike Thursday morning, officials said.
At least 36 people were transported to hospitals after the crash on President George Bush Turnpike in Irving, Texas, said Dr. Paul Pepe, Irving Fire Department's medical director.
At least three were in critical condition, Pepe said. Because many of the passengers were elderly, medical personnel are monitoring even those with minor injuries closely, said Pepe, who also is chair of emergency medicine at Dallas' Parkland Memorial Hospital.
The bus went off the right side of the road, hit a barrier, swerved left across lanes of traffic and struck a concrete median in a grassy area, Department of Public Safety Sgt. Lonny Haschel told CNN.
"It rode up on top of that concrete barrier, and then rolled on its right hand side where it came to rest," Haschel told CNN affiliate KTVT.
It was the only vehicle involved in the crash, he said.
The bus driver survived and was sent to a hospital, Pepe said.
The bus, owned by a Dallas-area charter company, was taking people to casinos in Oklahoma, said Nick Robison of Irving's emergency management office.
Video from KTVT showed a bus on its side, surrounded by numerous emergency personnel. Traffic on part of the toll road was halted as responders tended to the scene.
The National Transportation Safety Board said it has sent a team of investigators to the scene of the wreck.
CNN's John Branch and Jim Barnett contributed to this report.
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UPDATE (11:27 a.m.) - CNN reports that the wreck is on State Highway 161/President George Bush Turnpike near Belt Line Road where two people are confirmed dead and dozens are injured.
Initial reports said a bus rolled over in the crash and that as many as 40 patients may be trapped inside.
All lanes of the freeway on State Highway 161/President George Bush Turnpike between Belt Line and a tollbooth are being shut down.
Dozens of firefighters and other first responders are on the scene, searching inside the bus.
DART says the bus is not one of their vehicles and believes the bus is a private charter belonging to Cardinal Coach Line in Mansfield, TX.
This story is developing, but KMSS will continue to update it as more information comes in.