Investigators found no mechanical problems with the Greyhound bus that crashed in San Jose, killing two passengers.
California Highway Patrol Officer Chris Miceli says the investigation continues into the cause of Tuesday morning's accident on a rain-soaked Highway 101.
Eight other passengers and the driver were injured when the bus plowed into safety barrels and flipped on its side, coming to rest on the median divider. All are expected to survive.
Investigators earlier ruled out drugs or alcohol as a cause.
Miceli says the driver told investigators he was tired and had bought a cup of coffee at a stop about 30 miles before the accident.
The bus itself has been moved to Gilroy, to a bigger lot, so investigators can try and recreate what happened on Tuesday morning.
"The CHP team is re-constructing the scene," Capt. Spencer Boyce said. "Also doing mechanical inspections on the bus and interviewing passengers and potential witnesses to this."
They're also looking for clues inside the bus, focusing on where the passengers were seated.
"And then ascertaining the use of safety restraints," Boyce said. "The bus was equipped with safety restraints, but were they functioning properly?"
The driver has admitted being "fatigued." When asked about the driver's condition at the time of the crash, Boyce said Thursday he had no comment.