LAKE STEVENS - Manure-tainted runoff from chickens at an egg farm near here has tested positive for salmonella and fecal coliform bacteria. But officials think the bacteria will have dissipated before swimmers begin to use Lake Stevens this summer.

Dr. Mansour Samadpour, a University of Washington "bacteria hunter," tested polluted water last week that was taken from a ditch adjacent to the farm. He said it was "not at all" surprising to find salmonella in the samples.

Salmonella is a common food-borne cause of diarrhea in humans and can sometimes cause serious health problems or death.

Amberson Farms has been pressured by state and government agencies to clean up pollution problems on its egg farm. The owner caused an uproar among animal-welfare activists last week when he announced plans to kill the 50,000 hens on the property.

Amberson Farms is near Stevens Creek, a tributary of Lake Stevens.

Samadpour advised people to keep pets and children out of ditches and streams near Amberson Farms in the coming two weeks. He said the problem should eventually disappear.

"We don't expect this to be impacting the summer" activities on Lake Stevens, two miles south of the farm, Samadpour said.