Grisly discovery after family-of-four vanish during road trip

Searchers have found the body of a 12-year-old boy in a Northern California river - the last of four family members who died when their car plunged into a rain-swollen torrent.

The body of Siddhant Thottapilly was found about 4pm local time on Monday submerged in the Eel River about 9.5 kilometres downstream from where the family car reportedly crashed, Mendocino County Sheriff's Office Captain Gregory Van Patten said in a statement.

The body was found a day after the car with Siddhant's father and younger sister inside were pulled from the river sediment.

All four members of the Thottapilly family perished in the raging torrent of Eel River in northern California. Source: Facebook/Sandeep Thottapilly

A search team on a boat smelled gasoline about a kilometre downstream from where the crash was reported and found the Honda Pilot underwater, authorities said.

Inside were the bodies of Sandeep Thottapilly, 41, and nine-year-old Saachi Thottapilly.

The boy's mother, Soumya Thottapilly, 38, was found on Friday some way from the crash site in an area previously covered with water from the storm-swollen river.

The car crashed and plunged into the storm-swollen river. Source: Mendocino County Sheriff's Office

The Thottapillys were traveling from Portland, Oregon, to their home in the Los Angeles suburb of Santa Clarita when they were reported missing on April 8 after failing to show up for a visit with relatives in San Jose.

The crash site is about 322 kilometres north west of San Jose.

The driver apparently had pulled off the road during a powerful storm but the SUV went over the edge of an embankment into the flooded river, sheriff's officials have said.

Dozens of searchers had been combing the river with jet skis, boats and kayaks, along with dive teams.

Further south, authorities were still looking for the missing members of a different family whose SUV plunged off a towering ocean bluff along the Pacific Coast Highway last month.

Sarah and Jennifer Hart and their six adopted children were believed to be in the SUV at the time. Authorities say they believe the crash was intentional.

Five bodies were found March 26 near Mendocino, a few days after Washington state authorities began investigating the Harts for possible child neglect.

Three of the children have not been found. A body was pulled from the surf April 7 but has not been identified.