At about 10:15 a.m., a truck with an open top spilled gravel on the three left lanes of the highway just north of the Broadway exit, a California Highway Patrol officer said.
Big-rigs were allowed to use Interstate Highway 580 while the lanes were closed for the cleanup, according to the CHP.
At 11:18 a.m., the No. 3 and 4 lanes reopened, but traffic was backed up miles.
The CHP reopened all lanes just before noon.