The health and agriculture ministries said the cattle part in question was the thymus, which does not appear on a U.S. list of items that can be shipped to Japan.

Japanese government officials said the thymus is not considered at high risk of transmitting mad cow disease, and that the mistake was simply a case of improper paperwork.

But Japan still requested U.S. officials to conduct a thorough investigation and to take measures to prevent a recurrence, the officials said.

Tokyo will continue allowing beef imports from the 34 other certified meat processing plants in the United States.

Although the incident was considered minor, it did bring back memories of the fiasco that occurred in January this year just after Japan lifted the original ban on U.S. beef imports imposed after mad cow disease was confirmed in the United States.

Spinal cords were found in U.S. shipments, prompting Japan to reinstate the ban.

Japan resumed U.S. beef imports on July 27 this year.

According to officials at the Ministry of Health, Labor and Welfare and the Ministry of Agriculture, Forestry and Fisheries, the shipment with the thymus arrived at Osaka Port on Oct. 27 from a Swift & Co.'s beef processing plant in Greeley, Colorado.

When inspectors checked the shipment comprising 760 boxes (about 11 tons) of chilled beef and ox tongue at the Osaka branch of the agriculture ministry's Animal Quarantine Service on Oct. 30, they found a box containing 9 kilograms of cattle thymus.

The two ministries requested U.S. meat plants to compile a list of cattle parts eligible for export to Japan. That request was made to ensure conditions were met for the lifting of the import ban, including the removal of parts considered at high risk of transmitting mad cow disease.

Cattle thymus was not identified in the sanitary certificate issued by the U.S. Department of Agriculture.

U.S. officials said a shipping factory mistakenly included the box containing cattle thymus in the shipment to Japan. They promised to step up measures to confirm the contents at the time of shipment, Japanese government officials said.

Source: asahi.com