A 64-year-old Waipahu woman was killed Wednesday morning after the silver 2006 Dodge pickup truck she was driving leapt over a guardrail and rolled down an embankment on the H-1 freeway near Waimalu.

The Medical Examiner’s Office is awaiting identification of the woman by family members before releasing the information to the public. An autopsy is scheduled to be performed Thursday morning.

The pickup truck was heading toward town on the H-1 freeway just past the Kaahumanu Street overpass at about 8:20 a.m. when it veered to the right and struck the front bumper of another vehicle, the Honolulu Police Department’s Traffic Division’s Vehicular Homicide Section reported.

That caused a chain reaction involving a total of four vehicles.

Police said the truck spun 180 degrees after clipping the second vehicle.

The truck then went over the guardrail and rolled over several times down a grassy embankment. The truck landed roughly 40 feet below on its roof next to the Waimalu Drainage Canal behind Newtown Business Park.

The woman was thrown from the truck and died at the scene, police said.

The vehicle struck by the truck was pushed into a guardrail and then sideswiped a third vehicle, which collided with a fourth.

The drivers of the three other vehicles were uninjured, police said.

Traffic investigator Sgt. Scott Vierra said it is unknown whether speed or alcohol were factors in the crash.

This was the 49th Oahu traffic death so far this year, compared with 44 at the same time last year.

Police are asking for witnesses to come forward with any information about this case by calling the Traffic Division’s Vehicular Homicide Section at 723-3413.