The California Highway Patrol said 54-year-old Donald Bryant was found on the bridge's westbound incline at about 4:44 a.m. Saturday.
The CHP initially investigated the case as a possible hit-and-run but later classified it as an unexplained death and turned it over to the Oakland Police Department, police spokeswoman Danielle Bowman said.
The cause of Bryant's death will be determined by an autopsy by the Alameda County Coroner's Bureau. A coroner's spokesman said this morning the autopsy hasn't been completed yet.
Oakland police homicide investigators have begun a follow-up investigation into the death.
Police say that anyone with information about the incident should call the homicide section at (510) 238-3821.