SEATTLE - Washington state geoduck harvesters and government officials, including Gov. Jay Inslee, are scrambling to overturn China's decision to ban some shellfish exports from the Pacific Northwest.

The ban has brought the Peuget Sound geoduck industry to a virtual halt. Geoduck is a burrowing clam.

Fish inspectors in China notified the U.S. Embassy on Dec. 3 that China was suspending imports of geoduck and other "double-shell aquatic animals," such as oysters, because they found high levels of paralytic shellfish poisoning, or PSP, in a Nov. 21 shipment of geoducks.

PSP is a biotoxin produced by algae that shellfish eat and, in humans, in high levels it can lead to severe illness and even death.

The ban is a particularly ­nettlesome problem in ­Washington because China accounts for about 90 percent of geoduck exports from the state. And fisheries in the state harvest and farm 5.5 million to 7 million pounds of geoduck annually, according to Taylor Shellfish Farms, one of the state's largest geoduck providers. Those companies ­generally sell the clams for between $7 and $25 a pound.

The ban also affects Alaskan shellfish.

Washington fish companies are struggling to understand why the ban was imposed: Testing by the Washington Department of Health in the area where the geoduck ­shipments originated found PSP levels well below internationally accepted limits.

"We've gone back and looked at all records — they show results way below any human-health concern," Donn Moyer, a Health Department spokesman, said Saturday.

Geoduck harvesters believe the Chinese inspectors applied a standard for the level of ­toxicity that is well below what is considered safe for humans.

"The numbers I saw [that Chinese inspectors used] are just plain ridiculous," said Tony Forsman, general manager of Suquamish Seafoods, a Washington business run by the Suquamish Tribe.

To compound the challenge, communication from the Chinese government has been scant. State regulators and fishery executives say they have heard nothing more from the Chinese since the Dec. 3 notification. Media officials from the Chinese embassy in Washington, D.C., didn't respond to an e-mail query Saturday.

That has led the industry to turn to political leaders to resolve the issue. On Friday, Washington's governor and Commissioner of Public Lands Peter Goldmark sent a letter to the heads of the Food and Drug Administration and the National Oceanic and Atmospheric Administration asking them to engage in "direct interaction with the Chinese government" to determine the status of the ban and to gather information about the Chinese inspection.