REDONDO BEACH (CBS) — Cleanup crews returned Wednesday to the site where millions of small fish, primarily sardines, were found dead at Redondo Beach’s King Harbor.

Scientists say the fish suffocated due to lack of oxygen in the water. They say the fish were pushed into the harbor Monday by 45 mph wind gusts where they breathed all the available oxygen.

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The surface of the water is still covered in areas by tons of the approximately four-inch fish. In some locations, fish are a foot thick in the water. The clean-up operation is complicated by dead fish near or on the bottom of the harbor decomposing and floating to the surface.

Initial testing revealed no sign of natural toxins, such as domoic acid, which sometimes kills marine life. Most of the dead fish were in basins 1 and 2. City officials said there was no health hazard.

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No harbor area closures were issued Wednesday morning, but the Department of Public Works may close access for large construction equipment during the cleanup, city officials said.

Redondo Beach officials are also worried about tourism. They say with increasing temperatures, the stench from the dead fish will only increase and turn away harbor visitors.

The clean-up could take a week and may cost about $100,000 dollars.

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