Neuman was a veteran pilot and part-time aviation instructor at Orange Coast College. Baldwin, a Newport Beach real estate developer and an off-road racer, had invited TenEyck and Olavson to watch the Baja 1000 race, which Baldwin competed in Saturday.
Olavson was a developer based in Los Angeles. TenEyck, who grew up in Laguna Beach, lived in Wyoming.
An autopsy performed on the victims showed that they died of massive blunt trauma in the crash, Amormino said.
The pilot did not suffer a heart attack or any other medical emergency before crashing, Amormino said.
"Now it appears it [the cause of the crash] would either be mechanical or pilot error," Amormino said.
Neuman, who also was the chief flight instructor at Royal Aviation flight school in Costa Mesa, was described by friends and colleagues as an expert pilot with 17 years of teaching experience.
Federal Aviation Administration and National Transportation and Safety Board officials Wednesday searched the airplane for clues.
Tom Marquez, an FAA investigator, said the investigation into the cause of the crash is just beginning. The FAA is currently gathering every record they can find about the plane and the people on board, Marquez said.
Fifteen deep sea divers, from the sheriff's department and a private aviation salvage company, removed the men's bodies from the plane.
Witnesses reported seeing the plane spiraling downward, nose-first, into the water Saturday; the plane sank almost immediately and came to rest in 218 feet of water, officials said.
The single-engine, fixed-wing Cessna 210 took off from San Felipe, Mexico, and made a stop at San Diego's Brown Field Municipal Airport. It was bound for John Wayne Airport, U.S. Coast Guard Lt. Tony Migliorini said.
The plane is registered to a Newport Beach company, TR Builder Corp., owned by the father of one of the passengers, according to Federal Aviation Administration records.