Cleanup crews and environmental authorities are racing to contain the devastation linked to a large oil spill off the Southern California coastline as new concerns emerge over how the leak was handled in the critical hours after oil started spewing from a damaged pipeline.

The U.S. Coast Guard said Tuesday that about 4,000 feet of the pipeline had been displaced on the ocean floor. Divers found a 13 inch split in the structure, although they didn’t identify a possible cause. No oil was seen oozing from the pipeline at the...