(CNN) -- Police on Wednesday released the names of four women killed when a commercial tour bus ran off I-95 and overturned early Tuesday in Caroline County, Virginia.
The victims were identified as Karen Blyden-Decastro, 46, of Cambria Heights, New York; Sie Giok Giang, 63, of Philadelphia; Josefa Torres, 78, of Jamaica, New York; and Denny Estefany Martinez, 25, of Jersey City, New Jersey, according to a statement from Virginia State Police.
About 20 of the 53 people hurt in the crash remained hospitalized Wednesday for treatment of serious injuries at medical centers in Fredericksburg, Richmond and Hopewell, Virginia, police said.
Investigators blamed the accident on driver fatigue. The U.S. Department of Transportation prohibited bus company Sky Express Inc. from operating interstate transportation services. The Sky Express bus left Greensboro, North Carolina, on Monday at 10:30 p.m. and was en route to Chinatown in New York City. Sky Express is headquartered in Charlotte, North Carolina.
The driver of the bus, Kin Yiu Cheung, 37, of Flushing, New York, suffered minor injuries and was treated at the scene. Cheung has been charged with reckless driving and is being held on a $3,000 bond at the Pamunkey Regional Jail in Hanover County, Virginia.
The Virginia State Police Motor Carrier Safety Team ruled out any mechanical errors or malfunctions after inspecting the bus.
DOT's Federal Motor Carrier Safety Administration issued an unsatisfactory safety rating for Sky Express for violating multiple federal safety regulations for driver qualification requirements, drug and alcohol compliance, hours of service and vehicle maintenance.
The National Transportation Safety Board also is investigating.