KEMAH, Texas -

A Pre-Kindergarten student was injured recently on a school bus ride home, the girl's mother said.

The Clear Creek Independent School District, which covers the area near Kemah, is now investigating the April 11 incident.

"They did not have her in a car seat -- they were just using the seat belt. She is too small for just a seat belt," Emily O'Neal said.

O'Neal said her daughter, a student at Bay Elementary, received a concussion when she fell asleep and was jostled on the bus.

State law mandates any child younger than 8 years old must be secured in a federally-approved restraint seat, unless the child is at least 4 feet and 9 inches in height.

"She should have been in a seat. We're taking a closer look at what happened," said Elaina Polsen, a spokeswoman for CCISD.

Two employees, a school bus driver and a bus monitor, are on paid administrative leave pending the results of the investigation.

The girl appears to be making a full recovery. For now, her mother is driving her to Bay Elementary School.