A big rig overturned on northbound Interstate Highway 880 in San Leandro and went up in flames early Wednesday after its driver reportedly lost control of the truck.
The crash, which killed the driver, prompted the California Highway Patrol to issue a Sig-alert and close on- and off-ramps to I-880 near Davis Street.
Authorities believe the driver lost control and rammed the big rig into an embankment. The truck was reported to be on fire by 3:59 a.m., CHP officials said.
"There was one occupant who was inside and for unknown reasons wasn't able to exit the vehicle and is now deceased," said CHP Sgt. Brian Sams.
Hazmat crews were on scene as investigators tried to figure out what the tanker was carrying, as all identifying paperwork was burned beyond recognition in the fire.
Police originally believed the fluid could be baby oil, but later discovered that it was 1,800 gallons of refined, used motor oil.
Crews will excavate the contaminated soil and investigate whether the oil seeped into any of the nearby drains, which end up in the San Francisco Bay. The CHP does not consider this an immediate threat to the public.
"It doesn't seem like very much went down there," Sam said, "but it's a very thorough process to make sure none of it gets out to the bay."
The fire was contained shortly after 6:30 a.m, but the Davis Street on-ramp was expected to remain closed till 1 p.m. and the off-ramp through 8 p.m.