SEATTLE (AP) ― China has suspended imports of shellfish from the U.S. West Coast, cutting off one of the biggest export markets for Northwest companies and prompting fears of a months-long shutdown.

The Chinese government imposed the ban after discovering that recent shipments of geoduck clams from Northwest waters had high levels of arsenic and a toxin that causes paralytic shellfish poisoning, KUOW public radio reported

The Chinese government says the ban that started last week will continue indefinitely. Clams, oysters and all other two-shelled bivalves harvested off Washington, Oregon, Alaska and Northern California are affected.

“They’ve never done anything like that, where they would not allow shellfish from this entire area based on potentially two areas or maybe just one area. We don’t really know yet,” said Jerry Borchert of the Washington Department of Health told KUOW.

U.S. officials think the contaminated clams came from Washington or Alaska but are waiting for more details from China to help identify the exact source.

The National Oceanic and Atmospheric Administration will negotiate with the Chinese government on an agreement to reopen the shellfish trade. NOAA stopped issuing certification for shellfish exports last Friday.

The U.S. exported $68 million worth of geoduck clams last year ―most of which came from Washington state’s Puget Sound. Nearly 90 percent of those geoduck exports went to China.

“It’s had an incredible impact,” said George Hill, the geoduck harvest coordinator for Puget Sound’s Suquamish Tribe. “A couple thousand divers out of work right now.”

In the region, most geoduck farmers are based in Puget Sound, where about 2.3 million kilograms of wild geoduck are caught each year.

Geoduck sell for $100 to $150 per pound in China. Although the clams are harvested year-round, demand peaks during the holiday season leading up to the Chinese celebration of the lunar new year, which falls on Jan. 31 in 2014.

Officials say the closure could last for months. While the industry awaits a resolution at the international level, it is adjusting to the new reality.

A spokesman for Taylor Shellfish, the largest shellfish supplier in Washington, said the company is considering other solutions.

“I was just talking to our geoduck manager and he’s got two harvest crews and three beach crews essentially doing make-work,” Bill Dewey said. “He’s too nice a guy to lay them off during the holidays, but there’s only so much you can be charitable about making work for people and eventually you’re going to have to lay them off.”