MARSHALL, Calif. (AP) _ Oysters from one of the West Coast's richest mollusk spots have been pulled from restaurant menus after more than 100 people became sick.

Oyster harvesting from lucrative Tomales Bay beds has been suspended indefinitely as health officials investigate why 110 people became sick beginning in early May. An unknown contaminant was passed on to diners who complained of diarrhea, cramps, vomiting, low-grade fever and chills.

``We haven't had a California oyster in more than two weeks,'' said Steve Sancimino of San Francisco's venerable Swan Oyster Depot.

Sancimino and other restaurants are getting oysters from Puget Sound, British Columbia and other points in the Northwest. Even the Tomales Bay farmers are buying oysters out of state to resell to customers so they won't turn to other suppliers.

``We've got to carry on,'' said oyster farmer Mike Watchorn as he unloaded bags of oysters trucked in fresh overnight from Washington. ``These can't hold a candle to ours, but we have to stay in business for our customers.''

All Tomales Bay oysters were off the market by May 15.

Officials are surprised that the contaminated oysters come from one of the cleanest bodies of water on either coast. Tomales Bay, 37 miles northwest of San Francisco, is considered ideal because it's usually free of industrial contaminants and large vessels are too large to enter.

Tomales Bay oysters account for more than 80 percent of the $2.5 million-a-year Marin County shellfish industry.

Health officials say manure runoff from nearby dairy farms may be the source of contamination, but that usually happens after a rainstorm and these oysters were harvested during a dry period. It could also be human sewage dumped from a boat or a leak from a building, said Christopher Wogee, the state's lead specialist for seafood safety.

Meanwhile, many who enjoy the Tomales Bay oysters have had to do without. The Rev. Joan Hull normally has an open raw oyster bar at the annual Memorial Day barbecue she throws in Inverness.

``For most people it's their only opportunity to eat all the oysters they want,'' said Hull.

This year, her guests ate salmon.