Authorities say the vehicle went over the 18th Street overpass early Friday and landed on southbound Interstate 280, where it caught fire.
One person died after the Honda became wedged beneath the trailer early Wednesday morning, closing nearby streets during the investigation.
Investigators used genetic genealogy and dental records to confirm the identity of remains found near Sugarloaf Mountain in 1981.
Police say the driver was traveling 96 mph before striking multiple vehicles in a midday crash that left a pedestrian dead.
An Endangered Missing Person Advisory was issued across five Southern California counties as investigators asked for help locating the child and a suspect.
Authorities said the two-day sweep targeted people seeking illegal sex acts and crimes involving children in Northern Nevada.