Two lanes on the Pomona (60) Freeway in Jurupa Valley flooded amid heavy rain Monday, forcing motorists into the three remaining lanes, snarling traffic.
The obstruction was reported about 10 a.m. on the eastbound 60 at Pyrite Street, according to the California Highway Patrol.
The agency said the HOV and fast lanes were submerged, making them unusable.
As of 10:50 a.m., the blockage was not cleared, the CHP said.
Traffic was backed up for several miles. However, no SigAlert was in effect.
With heavy rain forecast to persist Monday, it was unknown whether the lanes would be reopened.