Thirteen people were thrown from the van, including four of the dead who were found in the median of Interstate 10 near Baton Rouge, Louisiana State Police spokesman Doug Cain said. The killed and injured were all aboard the GMC Safari minivan carrying 15 people, most of them children.
The crash occurred after the tire blew out on the van's front driver side, Cain said. The van then hit the delivery truck traveling in the same direction, rolled about 200 feet across the median and landed on its tires in the oncoming lanes. No other vehicles were involved.
"It appears the tire blew out and the driver overcorrected," said Trooper Russell Graham.
Only the driver, who was killed, and a front-seat passenger appear to have been wearing seatbelts, Cain said.
"The Louisiana Legislature just passed a law making it mandatory to wear seatbelts in both the front and back seats," Graham said. "This is a good illustration of why they did."
The 10 survivors were in critical condition Saturday afternoon at two Baton Rouge hospitals, Graham said.
The driver of the truck managed to steer to the side of the road and was not injured.
The interstate was closed in both directions for about three hours Saturday afternoon.
No identities were immediately released.