A 19-year-old Freeport woman died at a Houston hospital Saturday after being thrown from a motorcycle that was struck by a car Friday night.

Jessica Romero, who was a passenger on the motorcycle and wasn't wearing a helmet, suffered head injuries and was taken by helicopter to Memorial Hermann Hospital, Sgt. Corey Brinkman said. She died Saturday, a hospital spokeswoman said.

The accident remains under investigation, and a report was not yet complete Saturday, Brinkman said.

Romero was riding on the back of a 2005 Yamaha motorcycle driven by Juan Pina of Brazoria, whose age was unavailable Saturday, about 9:35 p.m. Friday, apparently leaving Brazosport High School's graduation ceremony at Hopper Field, Brinkman said. They were heading north in the 1700 block of Brazosport Boulevard when a southbound green 1996 Mercedes made a left-hand turn and struck the motorcycle, he said.

Pina, who was wearing a helmet, was taken by ambulance to Brazosport Regional Health System, but Brinkman said he did not know the extent of Pina's injuries. Pina was treated and released, a hospital spokeswoman said.

The driver of the Mercedes, Roderick Young, 28, of Houston, was cited for failure to yield the right of way to the motorcycle and for not having a valid driver's license or insurance, Brinkman said.

There also were two adult passengers and two child passengers in the car, he said. One of the children was taken to an area hospital for cuts to the head, Brinkman said. The child's name, age and gender were not clear, so a condition could not be obtained Saturday.