PORT HADLOCK — High levels of E. coli bacteria detected in a stream that enters Irondale Beach Park has prompted the closure of the tidelands south of Chimacum Creek to recreational shellfish harvesting.

The beach at Port Hadlock is open north of Chimacum Creek, said Michael Dawson, water quality lead for Jefferson County Environmental Health, reporting Friday on the state Department of Health announcement.

Neither swimming nor wading is recommended in the creek or on the beach.

Warning signs have been posted at the beach, stream and parking lot.

“Average bacteria counts were greater than 1,500 units per 100 milliliters, which is a very high number,” Dawson said.

Investigators are looking for the source, a process that includes checking for failing septic systems.

All area residents are urged to have their systems inspected, Dawson said in the statement.

E. coli bacteria occurs from fecal contamination in warm-blooded animals, including people.

They indicate the possible presence of pathogens that can make people sick.

The bacteria were discovered by monitoring conducted by the county public health department through the Northeast Jefferson Clean Water Project, which is funded in part by the state Department of Ecology.

Monitoring includes sampling from streams entering the shoreline along the Quimper Peninsula and Marrowstone Island.

According to the state Department of Health website at http://tinyurl.com/doh-wa-gov-beaches, marine biotoxins have prompted the closure of some beaches on the North Olympic Peninsula.

In Clallam County, Dungeness Bay and the Strait of Juan de Fuca from Pillar Point west to Cape Flattery is open for recreational harvest, while the area east of Pillar Point to the Jefferson County line, as well as Discovery Bay and Sequim Bay, are closed only to butter and varnish clam harvest.

In Jefferson County, Discovery Bay and Port Ludlow, including Mats Mats Bay, are closed to recreational harvest of butter and varnish clams, while Kilisut Harbor, including Mystery Bay, is closed for butter clams only.

Shellfish harvest also is not advised on the southern portion of Fort Flagler Spit, known as Rat Island, because of pollution from toxic substances.

Shellfish harvesting should be avoided from the eastern reaches of Fort Worden State Park beach and North Beach because the areas lie within sewage-treatment plant outfall closure zones, the state health department said.

Also closed are Old Fort Townsend beach, Pleasant Harbor Marina, Port Hadlock Marina and South Point Wilson.

All areas are closed for the recreational harvest of scallops.

Ocean beaches are closed to the recreational harvest of all species of shellfish from April 1 to Oct. 31 each year.