Mystery remains over cause of California oil pipeline leak

Workers in protective suits clean the contaminated beach after an oil spill in Newport Beach, California (AP)

Investigators searching for the cause of an oil pipeline rupture off the Southern California coast have pointed to the possibility that a ship anchor dragged the line across the seabed and cracked it.

However, two videos released so far provide only tantalising clues about what might have happened to the pipeline, owned by Amplify Energy, 100ft below the ocean surface, causing tens of thousands of gallons of crude oil to spill off the famed surf breaks of Huntington Beach.