"It's under investigation," Grossman said, noting that troopers at the scene worked through early Thursday and were still sorting out information.
Thursday evening, the driver and one child remained in critical but stable condition, said Lori Shaffer, a spokeswoman at Cooper University Hospital in Camden.
She said five other children remained hospitalized in stable condition. Three adults were treated and have been released, she said.
Grossman said the most serious of those injured was the driver, Sylvia Hernandez, 34, of Philadelphia.
The three other adults were identified by police as Luis Rios, 42; Rosa Torres-Baez, 23; and Veronica Rodriguez, 25, all of Philadelphia.
Police said the injured children included two boys, 8 and 7, and four girls, 10, 9, 8, and 5. All in the van appear to be related.
New Jersey law requires that all occupants wear seat belts and that all children younger than 8 or weighing less than 80 pounds have a car seat or booster.
Wednesday night, the highway quickly turned to chaos about 7:30 when Hernandez, heading west in the left lane, lost control of the vehicle, and it went off the road near mile marker 39 and rolled.
The accident closed the highway in both directions as three helicopters landed to bring the most seriously injured to Cooper's trauma unit, authorities said.
Contact Barbara Boyer at 856- 779-3838, email@example.com, or follow on Twitter @BBBoyer.