The California Highway Patrol was investigating a fatal head-on crash on Highway 84 at Thornton Avenue in Fremont late Tuesday night.
At least one person was dead after two cars collided just before 11 p.m., the CHP said.
Officers said that the accident was reported as having been caused by a driver traveling the wrong way, but they wouldn't confirm that. The specifics will not be confirmed until investigators at the scene have done so, they said.
One other perosn was taken to a hospital with minor injuries.
The westbound lanes of Highway 84 were closed as the CHP investigated. They were reopened around 1 a.m.
No further details were available.