At first, CHP believed the spilled substance was coal, but later learned it's petroleum coke, which is not considered dangerous.
All lanes of CA-4 have reopened, 511 Bay Area says.
UPDATE:Overturned Tractor Trailer blocks Left & Center Lanes on Eastbound CA-4 in Pittsburg.Estimated opening unknown.http://t.co/CH2jpbpZ7N
— 511 Bay Area (@511SFBay) May 16, 2015