The crash happened in the northbound lanes of the Fort Bend Tollway near FM 2234.
The Fort Bend County Sheriff’s Office said the two children, ages 4 and 8, were transported in critical condition. Pct. 4 Constable Trever Nehls said the 8-year-old has non-life-threatening injuries.
Deputies said three vehicles were involved in the crash near Lake Olympia. A silver Porsche with a flat tire was being followed by a relative’s family, a mother, father and their two children.
A utility truck struck the back of the family’s vehicle, deputies said. Then their car crashed in the Porsche in front of them.
The parents and the driver of the Porsche were also transported to a local hospital in an unknown condition. The driver of the truck was not injured.
Nehls said deputies did not find a child safety seat in the car for the 4-year-old.
The northbound lanes of the tollway were closed while investigators combed over the scene.