Beaches in King County were closed to shellfish harvesting last week by the Washington State Department of Health.

The ban was originally for only the area from Three Tree Point in Burien south to the Pierce County line.

Health officials acted after marine biotoxins that cause paralytic shellfish poisoning were detected at concentrations above the safe level in shellfish samples.

Commercially harvested shellfish are tested prior to distribution and should be safe to eat, the department noted.

The closure includes clams, oysters, mussels, scallops and other species of shellfish. Crab is not included in the closure, but the "crab butter" should be discarded, and only the meat should be eaten.

Fin fish found in these waters do not accumulate the toxins in their flesh and are safe to eat.

Marine biotoxins are not destroyed by cooking or freezing and can be life-threatening. Symptoms of paralytic shellfish poisoning may appear within minutes or hours and usually begins with tingling lips, tongue, hands and feet followed by difficulty breathing, and potentially death.

Any one experiencing these symptoms should contact a health care provider. For extreme reactions call 9-1-1.

The toxin is produced by naturally occurring "blooms" of microscopic plankton that tend to be more common during the warmer months of the year. The color of the water does not change and the plankton are invisible.

To check the latest shellfish harvesting closures, visit the marine biotoxin website at www.doh.wa.gov/ehp/sf/biotoxin.htm or call the Department of Health Biotoxin Hotline at 1-800-562-5632.