Updated

A minivan packed with 13 children and two adults was likely overweight and not designed to carry so many, police said Sunday, a day after the vehicle crashed on a highway, killing five.

State police said the minivan likely blew a tire and rolled Saturday on Interstate 10 near Baton Rouge. None of the children was wearing a seat belt and all were thrown from the vehicle, state police said.

Four children ages 2 to 14 were killed, along with the driver. State police spokesman Russell Graham did not have updates on the conditions of the injured children, and their names were not released.

Graham said the van didn't have enough seat belts for everyone. The driver and the other adult were wearing them, according to state police. Graham said the weight of the minivan "was probably more than it needed to be" and that it likely wasn't built to carry that many people.

"I just saw the vehicle flip about three or four times and kids flying everywhere," witness Tammy Hall told WAFB-TV. "It looked to be about 10 to 11 kids out of the car. ... You could tell the driver was dead instantly."

Police were still investigating and had spoken with family members, but it was unclear why there were so many in the van, and where they were headed, said Graham, who indicated those details weren't critical to the investigation.

"As far as the why, that's kind of outside the scope of our investigation," he said. "We look at the facts: there were that many kids in the car."

Authorities believe the tire blew, the van clipped a delivery truck and rolled. Officials were trying to determine how fast the vehicle was traveling. The driver of the truck was not injured and alcohol was not suspected as a factor, police said.

Graham said authorities believed most of the people in the van were somehow related, though he couldn't say how. He said all were believed to be from the Harvey, La., area.

Efforts by The Associated Press to reach family members were not immediately successful.

Two other children and the GMC Safari's adult passenger were in stable condition after the crash. The surviving children ranged from less than a year old to 14, police said.

Police identified the dead as the driver, 38-year-old Mona Hines; 2-year-old Ricky Hines Jr.; 12-year-old Lachante Floyd; 14-year-old Edward Barnes; and 14-year-old Ashley Hines.

"The Louisiana Legislature just passed a law making it mandatory to wear seat belts in both the front and back seats," Graham said. "This is a good illustration of why they did."