SEATTLE (AP) _ Thousands of dead fish littered a four-mile stretch of the Duwamish River on Sunday, apparently after sediment that washed into the river depleted the oxygen supply, a state Department of Ecology official said.

Witnesses said some people were carting home the easy catch, although experts warned against consuming the fish until the cause of the kill was verified.

All kinds of fish died, including flounder and salmon, witnesses said.

Craig Baker, district inspector for the state Department of Ecology, said the area stretched along four miles of the urban river.

He said bacteria in sediment that accumulated when the tide came in Saturday afternoon competed with the fish for the dissolved oxygen in the water. Low oxygen levels can stress or kill fish. Ecology department and utility officials were testing the oxygen levels in the water.

Baker said similar kills occur every year, but this was the largest he had seen in 15 years with the department.

''Most of the fish were making their way up the (Duwamish) river to spawn,'' said Baker, who toured the site by helicopter.

Asked how many fish died, Baker said, ''It's hard to guess, but we're talking about in the thousands.''

Mareatha Counts, a spokeswoman for Metro, Seattle-King County's sewage and transportation utility, said authorities were testing water and checking with industrial plants along the river. She said there was no indication that any abnormal activity from the plants contributed to the fish kill.