The marine biotoxin warning that shut down the shellfish harvest on the west side of Whidbey in August has been extended.

As of Monday, the closure extends from Maxwelton in the north to Ala Spit in the east, and still includes all of Deception Pass, according to the state Department of Health.

In August, the closure was located only from Fort Casey to Ala Spit.

Clams, mussels, oysters, geoducks and other shellfish should not be eaten if harvested from the affected waters. Crab is OK so long as it is thoroughly cleaned of its guts (also known as the “butter”) and are thrown away.

Cooking affected shellfish will not rid it of the toxin and can lead to adverse health effects like tingling of the lips and mouth, difficulty breathing, nausea or a sense of floating.

Symptoms can progress to loss of control of limbs, paralysis of the muscles used to breathe, or even death.

A type of phytoplankton is linked to paralytic shellfish poison, and although it is naturally occurring, it can rise to unsafe levels for humans. Affected water can still run clear although the condition is sometimes referred to as “red tide.”

It will be safe to eat shellfish from the affected areas once the advisory is lifted, as clean water will flush out the toxins in time.

The Department of Health’s shellfish closure does not have an end date yet, and seafood lovers should check its website before getting ready to crack a few shells.