The 210 Freeway east of Baseline Road was closed for several hours.
California Highway Patrol says the driver lost control of his vehicle on the westbound 210 Freeway around 1 p.m. and overturned, spilling a toxic material.
"We are still working on identifying it right now but believe it is hydrochloric acid, which is an extreme inhalation hazard," said CHP Officer Daniel Hesser. "What we did is take the precaution of moving everything away from the scene."
The cause of the crash is unknown.
CORRECTION: In an earlier version of our story, we wrote northbound and southbound lanes were closed. Westbound and eastbound lanes were closed.