Japan is trusting the U.S. Department of Agriculture to investigate why and how Tyson Fresh Meats Inc. exported a 35-pound box of spinal bones to the island nation.

Until it knows more, Japan is banning all exports from Tyson’s meatpacking plant in Lexington, NE.

As a defense against bovine spongiform encephalopathy (BSE), Japan bans shipment of spinal columns, skulls and brain tissue, eyes, and tonsils from cattle and only allows entry of beef from animals that are 20 months old or younger.

Forty-five other U.S. beef plants are exporting product to Japan under those restrictions, including seven others owned by Tyson.

The box of banned bovine spinal columns was one of 732 that arrived in Japan in late September and were being held in quarantine where inspectors discovered it last weekend.

A Tyson spokesman said the shipment of the box to Japan was merely a mix-up.

Tyson’s Lexington meatpacking plant was banned from shipping to Japan for four months during 2007 after it sent two boxes of beef to Tokyo that did not have written verifications that they came from young cattle as required.

The latest misstep comes at a bad time.  “It is extremely regrettable,” said Japan’s Agricultural Minister Hirotaka Akamatsu.  “We need to closely examine it it was just a careless mistake or if there is a systematic problem.”

Japan banned all U.S. beef in 2003 when a cow with BSE was found in Washington State.  Three years later, the ban was lifted with the new restrictions.  The U.S. was only recently trying to persuade Japan to ease the restrictions.

Tyson’s box of spinal bones was “an embarrassment” and an incident of “bad timing,” according to a Japanese Ag official.

U.S. trade officials have argued age restrictions are imposed by Japan without a scientific basis, and should be eliminated or at least raised to the more common 30 month and younger standard.

For now, however, Tyson will have to wait for the USDA investigation and work out “corrective measures” before its Nebraska plant can resume shipping to Japan.