A passenger bus that overturned Monday morning on I-95 North in Caroline County was traveling from North Carolina to New York, Gov. Bob McDonnell said Monday morning.

Four people were killed and more than 50 people injured in the crash, a quarter-mile south of the exit for Carmel Church.

McDonnell (R), who saw the aftermath of accident by helicopter, said I-95 will remain closed until about noon.

"The report I got at 9 was that it would be another couple of hours,’’ McDonnell said on his monthly call-in show on WTOP. “We would certainly hope by noon."

The commercial tour bus ran off the right side of the road and overturned, winding up completely upside down.

Virginia state police were called to the scene shortly before 5 a.m. The northbound lanes of I-95 remain blocked to allow teams to investigate the crash. Northbound traffic is being detoured at exit 98 in Hanover County, directed over to Route 1 and back to I-95 North at exit 110 in Caroline County. The lanes will remain closed through the morning rush.

McDonnell said it’s too soon to say whether there should be additional regulations on I-95.

“We don't know what happened with the accident,’’ he said. “We don't know anything about whether it was driver error, mechanical error whether someone forced them off the road. We just don't have that information. I'm not going to speculate on what else might be necessary."