A three-month-old B.C. boy was hurled out onto the interstate and had to be airlifted to hospital with serious head injuries after his mother's car rolled over in Washington State Thursday.

The 27-year-old Surrey mother and her three children were driving north on the I-5 near Marysville around 11 a.m. when she became distracted as her Honda SUV hit the rumble strip on the right-hand shoulder.

She told police that she over-corrected to the left, lost control and flipped the vehicle.

Her baby was ejected from the car in the wreck, and he and his car seat landed in two separate spots on the highway. Highway troopers believe that the infant was not properly secured in his seat, and the seat was not properly secured in the vehicle.

The baby boy was airlifted to Harborview Medical Center in Seattle.

The rest of the family was taken to Skagit Valley Hospital, where the mother is being treated for arm and head injuries, and a pair of six and seven-year-old sisters for minor injuries.

Police say the cause of the crash in under investigation, but drugs and alcohol were not factors.

For more information from the BCAA on correctly installing child car seats, click here.