BREMERTON — The Chinese ban of shellfish imports from the West Coast of the United States will continue indefinitely, according to a letter sent by Chinese officials to a U.S. agency.

The letter dated Jan. 23 was sent to the National Oceanic and Atmospheric Administration and raises new question about U.S. health standards for shellfish, the Kitsap Sun reported Saturday.

The letter dashes hopes of shellfish harvesters in Washington state who had hoped the ban would be lifted quickly after U.S. representatives submitted new information about safety standards along with test results that showed geoducks were safe.

China’s import ban is creating a hardship for the state’s shellfish industry. Geoducks are highly prized large burrowing clams that can fetch up to $50 a pound in Asian markets. The U.S. exported $68 million worth of geoduck clams in 2012, mostly from Washington state.

The letter from China clarifies the testing procedure used by Chinese authorities who found high levels of paralytic shellfish poison in geoducks harvested in Alaska. PSP, a neurotoxin produced by a type of plankton, can accumulate in shellfish.

The letter also asserts that a failure of Washington state officials to routinely test geoducks for arsenic “shows defects on regulating and monitoring the safety and hygiene for geoduck export to China.”

China’s ban was based in part on shipment of geoducks traced to Poverty Bay, near Federal Way, that the country said tested above its standard for inorganic arsenic.

Later sampling and testing by the Washington State Department of Health concluded that arsenic levels were safe — even according to Chinese standards. The tests did reveal elevated levels of arsenic in the skin of the giant clams, which state health officials said was typically discarded.

But the letter disputes that the skin is not eaten. “Chinese consumers eat the geoduck meat and skin and sometimes the digestive gland, too,” states the letter signed by Wang Xinwu of China’s General Administration of Quality Supervision, Inspection and Quarantine, or AQSIQ.

More information is needed before the Chinese government will consider lifting the import ban, perhaps keeping it in effect for a localized region, according to the letter. The Chinese official proposed sending an “expert team” to the U.S. to evaluate the regulatory system and negotiate an agreement for inspection, compliance and information exchange.

The Chinese letter tosses the issue back to the U.S., acknowledges a statement issued by the Office of Seafood Inspection, a branch of the National Oceanic and Atmospheric Administration. About 20 questions need to be answered from the U.S. side, including those dealing with testing and health-safety standards, according to the statement.

“Multiple state and federal agencies continue to be actively engaged in a coordinated effort to resolve this issue,” the NOAA statement said. “The states and federal agencies are working hard to answer China’s latest request for information so that U.S. companies can resume shipping these seafood products to China.”