Initially, Allman said the body was that of a child but the sheriff's office later corrected that it was a woman's.
The family of four - two parents and two children - was traveling from Portland, Oregon, to their home in Santa Clarita, California, last week when they stopped communicating with relatives.
A search team found the body about 7 miles south of where the family's SUV Mendocino County Sheriff Thomas Allman told a news conference in the community of Leggett.
The body has been sent for identification, amidst fear that that this could be that from the missing Thottapilly family.
Five bodies were found March 26 near the small city of Mendocino, a few days after Washington state authorities began investigating the Harts for possible child neglect, but three of their children were not immediately recovered from the scene.
"Preliminary results showed Jennifer Hart had a.102 BAC (blood alcohol content)", the Mendocino County Sheriff's Office said in a statement on Friday.
The vehicle is reported to have submerged in the river around 1:10 pm on April 6.
Crews have not yet actually located the vehicle.
It said several items were identified by the family members of those missing.
On Thursday, the Mendocino County Sheriff's Office said it had found belongings of the Thottapilly family, of Santa Clarita, as well as vehicle parts from their SUV about 14 miles down river from where investigators believe they rolled down an embankment.
Two more are missing and another body has been found but not identified. "These items were of a personal nature and will not be described further at this time, but it does confirm the fact the vehicle that was seen going into the river was that of the Thottapilly family".
Authorities have said data from the vehicle's software suggested the crash was deliberate, though the California Highway Patrol has not concluded why the vehicle went off an ocean overlook on a rugged part of coastline.
The family was last heard from in the town of Klamath, Del Norte County, on April 5.
The family was officially reported as missing to the San Jose Police Department on April 8.
Officials said Friday that witnesses saw the family's Honda Pilot pull into a turnout alongside the river in the midst of a rainstorm a week ago.
