Millions of dead fish were found in a marina in Los Angeles, California, a media report said.
Authorities were trying hard to clean up the area as the surprising situation Tuesday made for memorable sights such as dozens of boats floating on a sea of dead fish a foot deep, the Los Angeles Times said on its website.
Preliminary reports by experts suggest "deprivation of oxygen" as the cause of the fish kill, but so far there is no proof that the situation has an "environmental" cause, officials said.
In principle, the massive gathering of fish in a relatively small enclosed area could result in a lack of oxygen in the water there, but officials said that they are conducting tests of the water in the marina to determine if there might be toxins, oil or chemicals in the water that could harm sea life.
Although it's not certain yet, the cause might be the appearance of an elevated number of algae in the area, if higher concentrations of oxygen in the water can be proven, University of Southern California researchers said.
The massive presence of algae in an area of water results not only in higher oxygen consumption there but also produces toxins that could prove fatal for marine life, David Caron, a professor at the university, said.