'Millions' of dead fish surface in Redondo Beach marina

US officials fear a public health hazard after millions of small dead fish that washed up in a California marina begin to rot.

The anchovies, sardines and mackerel coated the surface of the King Harbor Marina in Redondo Beach, near Los Angeles, attracting flocks of birds.

The BBC's Rajesh Mirchandani explains what scientists think caused the phenomenon.