Updated

At least four people were killed and several injured when a bus overturned early Tuesday in central Virginia, MyFoxDC.com reports.

Sgt. Thomas Molnar says 57 people were on board, including the driver. The injured were taken to Richmond and Fredericksburg-area hospitals, according to the station.

State police spokeswoman Corinne Geller said the bus ran off northbound I-95 and turned onto its roof about a quarter mile south of the Carmel Church exit, about 30 miles north of Richmond.

The driver suffered minor injuries and is cooperating with investigators who are trying to determine what caused the crash, Molnar said.

Officials haven't released the name of the bus operator, the starting point of the trip or its destination.

Virginia Commonwealth University Medical Center has nine people in stable condition, but no details were released about the extent of their injuries. VCU spokeswoman Anne Buckley says the hospital expects more patients to be transferred there from other hospitals.

Mary Washington Hospital in Fredericksburg treated eight patients, whose injuries ranged from critical to minor. Spokeswoman Deborah Morris says one has been released. Spotsylvania Regional Medical Center officials said in a release that it treated eight people for minor injuries.

The accident shut down the northbound lanes of I-95, which weren't expected to reopen for several hours.

The crash comes about two and a half months after a horrific New York City accident that focused attention on bus safety. In that March 12 crash, a speeding bus returning from a Connecticut casino toppled off an elevated highway and hit a utility pole, peeling off the roof. Fifteen passengers were killed and 18 injured.

The Associated Press contributed to this report

4 Dead after Passenger Bus Overturns On I-95 in Virginia: MyFoxDC.com