National Transportation Safety Board Chairwoman Deborah A.P. Hersman disclosed the new information during a U.S. Senate committee hearing in Washington on motor coach safety Wednesday.
She also said that a video camera on the motor coach windshield "did not record the accident."
The bush crashed March 12 while returning to the city from a casino in Connecticut. The bus flipped onto one side and struck a pole, which nearly severed the roof off.
An attorney for the driver, Ophadel Williams, did not immediately respond to a request for comment Wednesday. The driver has not been charged.