State police and the sheriff's office continued searching the Cherrystone Family Camping Resort on Chesapeake Bay for any additional casualties, Geller said.
Those injured by the storm in Northampton County have been transported to nearby hospitals, according to Geller.
Others staying at the campground were transported by bus to a local school set up as a temporary shelter, she added.
The National Weather Service said a cluster of "supercells" ahead of a cold front formed a storm over Chesapeake Bay just after 8 a.m. ET.
According to the weather service, the storm intensified as it moved on ashore about 30 minutes later.
Photos from the scene showed overturned campers, with a downed tree crushing one vehicle.
The campground that opened in 1964 occupies 300 acres with 725 sites including cabins, cottages, and deluxe campers, its website says.